A massive earthquake off the coast of Indonesia has killed hundreds of people and triggered tsunami alerts around the Indian Ocean.
The 8.7 magnitude quake struck just before midnight, destroying buildings on the Sumatra island of Nias.
Thousands of people fled their homes in Indonesia, Malaysia, Thailand, India and Sri Lanka - areas still recovering from the deadly tsunami in December.
But three hours after the quake, tsunami alerts were scaled down.
Vice-President Jusuf Kalla told the BBC he feared up to 2,000 people may have died on Nias, not far from the epicentre.
But he said this figure was based on an assessment of damaged buildings, not a body count. Local officials said about 300 people were feared dead.
Around 80% of buildings had been affected in the town of Gunungsitoli, Mr Kalla said.
Indonesian President Susilo Bambang Yudhoyono postponed a planned trip to Australia and said he would fly to the island to assess the damage.
"We are busy now trying to pull people or bodies of children from the collapsed building," said a police officer on Nias. "It is very hard also because there is no power."
Agus Mendrofa, deputy mayor of Gunungsitoli, told Indonesian TV: "Gunungsitoli is now like a dead town. The situation here is in extreme panic."
Nias lies about 200km (125 miles) off the Sumatran mainland, and to the south of the province of Aceh, the area worst affected by December's tsunami.
In Indonesia's Aceh province, people fled for higher ground
A Christian missionary working outside the town said hundreds of wounded had come to the mission seeking help.
The tremor struck at around 2315 local time (1615 GMT) and lasted up to three minutes, Indonesian monitors said.
The 26 December tsunami killed an estimated 300,000 people in a dozen countries - two-thirds of them in Indonesia.
"It seems [Monday's] earthquake did not trigger a tsunami," Prihar Yadi, a scientist with the Indonesian Geophysics Agency, told AP.
"And if there's no tsunami on the coastline near the epicentre... there will not be one heading in the other direction."
In Aceh province, an aid worker for Christian charity Tearfund, Jon Kennedy, said the ground had "swayed".
"It was simply huge - we ran into the street," he said.
Aceh people say the tremors have been getting progressively stronger over the past couple of weeks.
US Geological Survey spokesman Don Blakeman told Reuters news agency that while Monday's quake was an after-shock of the earlier quake, which had a magnitude of 9, it was also a "very serious earthquake in its own right".
In the Malaysian capital Kuala Lumpur, some 500km from the epicentre, high-rise buildings were evacuated and people ran into the streets.
"I was getting ready for bed, and suddenly, the room started shaking," said Kuala Lumpur resident Jessie Chong.
Thailand and India, badly hit by the December disaster, temporarily issued tsunami alerts while Sri Lanka evacuated coastal areas.
"It was like reliving the same horror of three months ago," said Sri Lankan Fatheena Faleel.