Several countries around the Indian Ocean have been hit by devastating sea surges. The BBC's correspondents report from the affected areas as rescue attempts begin.
Monday 27 December
Andrew Harding : Phuket, Thailand : 2220 GMT
The death toll has leapt up enormously - in the last few hours alone it has more than doubled to nearly 1,000. The trouble is this isn't a straight, smooth coastline. There are lots of inlets, there are mangrove swamps, places where bodies could easily be hidden and of course there are also many islands of the coast which were hit particularly hard by the waves and are particularly inaccessible.
Geeta Pandey : Andaman Islands, Indian Ocean : 2213 GMT
Officials are saying at least 3,000 people died and an equal number are missing. In the capital, Port Blair, there have been more tremors in the last few hours and we all ran out of our homes and offices. I have seen a lot of people sleeping in the streets.
Nick Bryant : Colombo, Sri Lanka : 2208 GMT
All across this city hotel lobbies are jam packed with tourists trying to leave the country. They have been bussed up from the worst affected areas but many have arrived without passports and plane tickets which were simply washed away. But the people of Sri Lanka themselves are bearing the brunt of the catastrophe. The government admits it cannot cope alone.
Laura Trevelyan : New York, USA : 1921 GMT
Billions of dollars of damage have been caused by the Asian tidal wave, according to the UN's emergency relief co-ordinator, Jan Egeland. He says it could be the costliest disaster in history.
Mr Egeland, speaking to reporters at UN Headquarters in New York, predicted that hundreds of aeroplanes carrying relief supplies would be arriving in the countries affected in the next 48 hours.
Tim Johnston : Jakarta, Indonesia : 1655 GMT
The authorities are just getting through to some of the places worst affected by the earthquake.
Up on the northern tip of Sumatra, close to the epicentre of the quake, the regional capital Banda Aceh has been devastated.
Aid has only just reached some of Indonesia's worst-hit areas
A relatively small town, some estimates say that as many as 3,000 people might have died there, and government officials who visited on Monday said large numbers of bodies were still lying in the streets.
And there has been no news yet from the western coast of the island, the area closest to the earthquake.
Roland Buerk : Galle, Sri Lanka : 1645 GMT
Along Sri Lanka's coast, people have spent the day digging in the mud and the ruins.
They've unearthed body after body and, as quickly as they've been found, they've been buried again.
Death has cast so wide a swathe through towns and villages here, there has been little time for ceremony for those who have been lost.
Ishbel Matheson : Nairobi, Kenya : 1555 GMT
It seems the north-western area of Somalia, Puntland, was worst hit. Many fishermen who ply the warm waters of the Indian Ocean in flimsy, handmade boats simply did not return home.
A minister for the new Somali government based in Nairobi said many houses had been damaged and thousands were now homeless.
Kylie Morris : Phuket, Thailand : 1555 GMT
Phi Phi was swamped by the mass surge of water on Sunday. Officials say they'll begin to collect the bodies of the dead once they've taken care of the living.
For the moment, bodies are being laid out in makeshift morgues in village temples.
Matthew Grant : Madras, southern India : 1520 GMT
Most of the people in this part of the world are Hindus, who cremate their dead. But there have also been reports of bodies being buried in mass graves, because people just can't cope in any other way.
Sanjeev Srivastava : Delhi : 1440 GMT
The government is doing all it can to save a situation which is becoming grimmer by the hour.
Infrastructure damage is still being assessed across the region
They have asked everybody to stay away from low-lying areas till further notice, but in several parts of southern India evacuation and relief work has been hampered by heavy rains.
The state owned Indian Airlines is operating special flights to the Andaman and Nicobar Islands to airlift tourists stranded there. Four ships carrying a team of doctors, food and other relief material have also been sent to the Andaman and Nicobar Islands.
Roland Buerk : Galle, Sri Lanka : 1420 GMT
The damage is really quite extraordinary. All day today people have been digging in the mud and ruins, unearthing bodies. There have been some very rapid funerals taking place.
Mostly people here are having to help themselves. The military helicopters coming in from time to time can only airlift out about five people at a time. Most other people have gone up to the coastal road to try to walk to Galle.
Now night has fallen it is completely dark; electricity is cut off. Armed soldiers have set up road blocks to try to keep order.
Navdip Dhariwal : Galle, Sri Lanka : 1325 GMT
The government has deployed 10 helicopters to drop rescue teams to the worst affected areas. Over 25,000 soldiers have rushed to the coast, but their efforts appear to be making little difference.
With power and communication lines down, it's still difficult to travel around the island or get information. The government is reporting that 200 foreign tourists are now among those dead.
Those left here are anxious to leave, not out of fear of secondary shock waves, but out of concern they will be abandoned without electricity and water.
Geeta Pandey : Andaman Islands, Indian Ocean : 1215 GMT
I've seen several hundred people staying in a school building which has been turned into a makeshift shelter. A lot of people are complaining that they are not getting enough food.
Survivors of the surges have begun to bury their dead
And for many of the islanders, a lifetime of savings have disappeared in a few seconds before their eyes.
So there's a lot of apprehension and fear about what the future will be like.
Medical supplies have been sent out to the islands, and an aerial survey of the situation is being carried out right now.
Kylie Morris : Phuket, Thailand : 1155 GMT
There's a scene of complete devastation on what was the idyllic Phi Phi island. The deputy governor says it's likely more than 100 have died there.
As many as 800 people remain stranded in hills on the island. Thailand's prime minister has appealed on national television for blood donors and for money.
Chris Hogg : Bangkok : 1100 GMT
Provincial officials say the priority now is to find those who are still injured and stranded. On Phi Phi island near Phuket, almost everything apart from the major hotels has been destroyed.
Officials suggest at least a third of those killed were foreign tourists.
Rachel Harvey : Medan, Indonesia : 1045 GMT
There's a whole area on the south west coast of Aceh, closest to the epicentre of the earthquake, where there's been no contact at all. Officials are increasingly concerned about the situation there.
It's thought there were a million people living in that area.
Rachel Harvey : Medan, Indonesia : 1020 GMT
Relief supplies are beginning to arrive in the Sumatran city of Medan ready for transport into the affected area.
The priority now is to help the injured and stranded
But the Indonesian government has yet to decide whether to allow international aid agencies to operate in Aceh.
The province has been virtually sealed off for the past 18 months because of a conflict between Indonesian security forces and separatist rebels.
It seems likely that help will in the end be accepted, but time is now critical.
Gina Wilkinson : Colombo, Sri Lanka : 0755 GMT
The worst hit regions are on the east coast - where tsunamis wiped out entire villages and fishing communities.
Land mines laid during the civil war were dislodged by
flood waters and are floating off beaches and in lagoons - hampering rescue efforts.
Kylie Morris : Phuket, Thailand : 0755 GMT
The government has warned it expects the casualty figures will continue to rise as rescue workers reach outlying resorts.
The scale of the damage is yet to emerge
Among the dead are tourists from as many as 12 nations. Many Thai fishermen are still missing.
To compound the sense of tragedy here, local officials have confirmed that a grandson of the country's much loved King is among the victims.
Navdip Dhariwal : Galle, Sri Lanka : 0702 GMT
In the ancient port town of Galle it's a picture of devastation.
Local people here are walking the streets looking dazed and confused.
Debris from buildings lies scattered on the streets. Overturned cars and buses and trucks are stacked up on the roadside.
Eyewitnesses say two tidal waves struck the town early yesterday morning. The force of the second wave was so strong it threw people and vehicles in its path.
Dumeetha Luthra : Colombo, Sri Lanka : 0652 GMT
The scale of the tragedy has left Sri Lanka reeling. It has never experienced anything like this before.
The south of the island and the north-eastern coast have borne the brunt of the waves, exactly where scores of tourists had travelled for some Christmas sun.
It was a record year for Sri Lanka's tourist industry. The majority of hotels along the southern coast were fully booked, filled with local and foreign holidaymakers.
Chris Hogg : Bangkok, Thailand : 0534 GMT
A clearer picture of the scale of the damage is starting to emerge.
Prime Minister Thaksin Shinawatra told reporters helicopters and ships from the country's armed forces have been deployed to help evacuate outlying islands.
Several thousand tourists and local people were still stranded in the worst affected areas.
He said he had asked the military to prepare 1,000 body bags. Reports from Phuket say almost a third of the corpses laid out in a car park at one of the island's hospitals were tourists.
Many were still wearing their swimwear.
Matthew Grant : Tamil Nadu, southern India : 0421 GMT
In the city of Madras, homeless people who spent the night in shelters were often too scared to sleep as they feared aftershocks and fresh tidal waves.
The first reports are also emerging from some of the more remote fishing villages up and down the coast.
People reaching them are describing finding scores of bodies left on the beaches.
Chris Hogg : Bangkok, Thailand : 0343 GMT
Police and volunteers on the Thai island of Phuket are manning barricades to try to prevent looting.
Officials have so far provided little information about the nationalities of those who died there but local media suggest a sizeable number of those killed were Western or Asian holidaymakers.
Kylie Morris : Phuket, Thailand : 0137 GMT
Most of the tourists who had flocked to the main beaches of Phuket for their Christmas holiday have now been removed to safer areas or are trying to leave the island on flights to Bangkok.
Many at the airport spoke of traumatic experiences. One Australian tourist told me he'd unsuccessfully tried to resuscitate a Thai boy.
The Thai military are helping to evacuate the injured
A British woman spoke of seeing children torn from their mother's grip in the surging waters, an Israeli diver of the anxious wait amidst enormous swells out to sea.
The Thai government has asked local people not to use their mobile phones in order to reduce congestion.
Hospitals are flying in extra doctors to perform surgery on the broken arms and legs of those swept up by the surging waves.
Helicopters, naval frigates and fishing boats are expected to resume their attempts to reach some outlying resorts.
There's particular concern over the fate of foreign travellers who had ventured to isolated beaches on Phi Phi island and in other remote areas of Krabi.
Diplomatic missions are establishing outposts in an attempt to provide consular assistance to tourists.
However, they face a difficult task. Many of those who travel to the Andaman coast are in search of a secluded beach holiday. Their isolation will make them all the more difficult to trace.
Sunday 26 December
Chris Hogg : Bangkok, Thailand : 2335 GMT
As rescue efforts continued throughout the hours of darkness, officials in the countries worst affected were still trying to get a more accurate picture of what needs to be done now.
The fear is that as communications begin to be re-established and the emergency services reach the more remote communities the true scale of the devastation will prove much worse than they had feared.
Matthew Grant : Madras, India : 2007 GMT
Many people were out walking or playing cricket on the beaches of Madras when the tidal wave struck. Police have recovered hundreds of bodies from the city and along the coast.
Others have been washed ashore. Some were thrown into lorries while others were carried to hospital on carts or in sacks.
Locals say they felt the rumble of the earthquake early this morning from its epicentre thousands of miles away in the Indian Ocean.
Then, just over an hour later came what they describe as the wall of water. It slammed into the coastline.
It's now dark in Madras and most of the water's gone back out to sea but along the coast there's still signs of devastation.
Many of the roads there are closed and strewn with debris. Some of the shanty towns by the beaches are completely destroyed and out to see hundreds of fishermen are still believed to be missing.
Kylie Morris : Phuket, Thailand : 1635 GMT
I've just arrived at Phuket's airport where there are chaotic scenes. Hundreds of tourists are trying to leave.
Many British people on group holidays are desperate to get off the island and back to Bangkok.
Tourists are desperate to leave Phuket and get home
Many individual stories of bravery and terror are emerging. One man told me he had tried and failed to resuscitate a young Thai boy.
I just met a couple at the airport who were leaving without their passport, without any of their belongings.
They had been swept from their hotel room after being given five minutes warning to get out. They couldn't get out in time.
The husband tried to hold onto his wife as long as he possibly could. She was swept away.
He caught up with her again, but he burnt his hands when he grabbed hold of electrical wires to try and brace himself against the waters.
Sanjeev Srivastava : Delhi, India : 1615 GMT
There was no warning at all, which makes this tragedy unexplainable in the eyes of many people.
This part of the country is used to cyclones. There are a substantial number of people killed every year because of these.
Either because they can't move in time, or they are too poor to move.
But this tragedy has not differentiated between the rich and poor.
In some cases the more well-to-do have suffered more as they were on the beaches, or travelling as tourists.
Rachel Harvey : Jakarta, Indonesia : 1510 GMT
We've now had a sudden leap in the official casualty figures, which now stand at 1,847 people dead.
The worst affected part of Indonesia is Aceh, a province which has been sealed off for the last 18 months because of an ongoing conflict between the government and separatist rebels.
But it now seems clear that they're going to have to open up this province in order to allow the relief effort in.
Gina Wilkinson : Colombo, Sri Lanka : 1430 GMT
In the district of Trincomalee on the east coast, military officials say tsunami waves swept more than two kilometres inland washing away entire villages.
The injured are being moved inland amid fears of more tsunamis. President Chandrika Kumaratunga has declared a state of national disaster and is appealing for help from the international community.
Sanjeev Srivastava : Delhi, India : 1325 GMT
A number of cities have been badly hit. One is the town of Velakanni, a small fishing village in Tamil Nadu which is also a pilgrim town. It is famous for its church. A number of pilgrims were taking a bath in the holy waters there.
400 or maybe 500 of them have drowned in those waters. But the numbers are pure guesswork at the moment.
Andrew Harding : Singapore : 1255 GMT
Some felt the quake first, others saw the sea sucked away from beaches only to return minutes later as a wall of water up to 30 feet high. The tsunamis have left a ring of devastation around the Indian Ocean, giant ripples travelling at the speed of a jet.
There have been more aftershocks but none as big as the original quake. The focus now is on searching for survivors and for bodies, and waiting to see if thousands of fishing boats will ever come home.
Navdip Dhariwal : Delhi, India : 1215 GMT
Madras's beaches were full when the waves struck
The state of Tamil Nadu has been worst hit after tidal waves lashed the south-eastern coast line.
Crashing waves rising almost two feet have trapped 500 tourists on a Rock memorial and a nuclear reactor has been forced to close down.
The Indian prime minister has put the Army, Navy and Air Force on full alert.
Gina Wilkinson : Colombo, Sri Lanka : 1120 GMT
A military spokesman says damage from the tsunami wave stretches all the way from Jaffna in the north of Sri Lanka to the popular beaches in the south.
More than ten thousand military personnel, backed by naval vessels and helicopters are combing the coastline searching for survivors and pulling bodies from the sea.
In the district of Trincolome on the east coast officials say massive waves have dislodged landmines laid during the country's civil war hampering rescue efforts.
In the southern town of Maderapu police say more than 100 people died when a tsunami hit a weekend market, washing shoppers and vehicles out to sea.
There's also been extensive damage at a string of tourist resorts on the south coast packed with local and foreign holidaymakers.
Officials say they expect the death toll to rise, communications problems in some parts of the island are slowing efforts to assess the full scope of the disaster.
Sampath Kumar : Madras, India : 1115 GMT
Madras has one of the most beautiful beaches in India, stretching more than seven kilometres. Being a Sunday, many people were jogging, walking and exercising on the beach, while some were in the swimming.
All of a sudden, huge columns of water surged towards the land without any warning. Most of the people were caught unawares and had to run for their lives.
Eyewitnesses say that it appeared as though the entire sea was rushing towards them. The water rose to nearly 200 feet.
Fishermen living by the water say enormous columns of water swept their huts, boats and fishing nets.
Most of the dead are from fishermen and the worst affected area is in the heart of the city.
Matthew Grant : Calcutta, India : 0845 GMT
The police chief in Madras, the capital of Tamil Nadu, said at least 100 bodies had been recovered from beaches in the city. Most of them were women and children.
The waves struck without warning
Another hundred people are believed to have lost their lives as a result of the tsunami elsewhere in the state.
The impact of the quake was felt right along India's southern and eastern coasts. Many villages have been evacuated and fishermen have been warned not to venture into the sea.
Kylie Morris : Bangkok, Thailand : 0800 GMT
The worst hit area is the holiday coast of southern and eastern Sri Lanka where the national disaster management centre says five hundred people are feared dead.
In southern India officials say hundreds of fishermen are missing. Rescue workers in Thailand say tourists in the resort of Phuket who had begun their Boxing Day with a morning swim were swept out to sea by the surging, towering waves.
In Indonesia, the troubled province of Aceh, in northern Sumatra, was closest to the epicentre of the earthquake where a local mayor said more than sixty people had drowned and hundreds of houses were swept away.
Roland Buerk : Moratuwa, Sri Lanka: 0750 GMT
The tidal wave struck without warning. A surge of water swept through beachfront hotels. There were loud crashes as buildings collapsed.
Everything, cars, tables, refrigerators and people were swept along by the current. I grabbed hold of a tree. When that came down I was swimming for my life until I managed to get hold of a pillar.
The waters here have now begun to recede slowly. They are leaving behind widespread devastation. People are digging through the ruins looking for loved ones.
Bodies are being pulled out and many of the survivors are wandering around in shock. Here, at least, rescuers are yet to arrive.