Iran has appealed for medicine and equipment to help tens of thousands hurt in Friday's devastating earthquake in the south-eastern town of Bam.
Thousands left homeless need shelter and supplies
The plea came as the first special international rescue teams arrived in the country to search for survivors.
Estimates of numbers killed in the disaster range from 10,000 to 25,000.
The Iranian authorities say more than 5,000 bodies have already been buried in mass graves, and hopes are dwindling for anyone who might be still trapped.
Many thousands of people have been injured and most of Bam's buildings have been flattened, including two hospitals and the old citadel.
One official said 150 people had been pulled out alive from the rubble on Saturday, including a baby less than a year old.
The BBC's Jim Muir says thousands of people spent a second night keeping well away from any of the buildings still standing for fear that an aftershock might bring them down.
They slept in tents or cars or simply huddled in blankets out in the open.
Our correspondent says work began again on digging through the ruins at first light on Sunday, and it was not long before the bodies of more entire families buried in their sleep began to emerge from the rubble.
But the main priority now is to provide food, clean water and shelter for those that are left in the city.
Rescuers say there is also an urgent lack of body bags to take away the corpses.
The exact death toll is not clear, but some local officials say it is much lower than media reports were suggesting.
Whole buildings simply crumbled to the ground
The regional governor said 5,500 dead had been buried by the end of Saturday.
Nations around the world have reacted swiftly, sending rescuers, doctors, tents and cash to the stricken region.
President George W Bush said the US was ready to help, and Iran has said it will accept aid from any country except Israel.
The US will send emergency teams and medical supplies, and senior officials from Washington and Tehran have been in touch over the crisis.
But a spokesman said there was "no political angle" to the dialogue between the two countries, which have not had diplomatic relations since the Islamic Revolution of 1979.
Iranian Health Minister Ahmed Pezeshkian said more foreign volunteers were not really needed because Iran was having trouble co-ordinating its efforts.
He said Iran had already had large numbers of local volunteers coming in from all over the country.
Instead it needed medical equipment like mobile x-ray machines and ventilators.
The International Red Cross has launched an appeal for $12m of aid for the huge numbers made homeless by the earthquake, but it says appeal target amount is likely to rise in the next few days to meet survivors' long-term needs.
The European Union has pledged almost $1m in aid to Iran.
The United Nations is sending experts to assess the damage and mobilise international assistance.
RECENT IRAN QUAKES
June 2002: more than 200 killed in the western Qasvin and Hamedan regions
May 1997: More than 1,500 killed in eastern Iran
February 1997: about 1,000 killed in north-western Iran
June 1990: About 40,000 died in Iran's worst recorded disaster, affecting Caspian areas of Gilan
and Zanjan. About half a million people made homeless
June 1981: More than 1,000 killed in quake that destroyed town of Golbaf
For those who are alive, the Red Cross says tens of thousands of tents, blankets and tarpaulin sheets are needed as well as cooking equipment, water purifying tablets and kerosene.
The only hospitals still functioning in Bam have been overwhelmed by the numbers of injured and many people are being treated in the rubble-strewn streets or taken to other towns for treatment.
Dozens of Iranian military planes have been mobilised to evacuate the wounded from the earthquake-hit zone to hospitals in Tehran and other cities.
President Mohammad Khatami described the quake as a "national tragedy" and said it was too huge for Iran to cope with alone.
Bam and the surrounding area is home to more than 200,000 people.
Most of the destroyed structures were made of mudbrick or ordinary bricks which collapsed in a heap, leaving no protected spaces where people might survive.
Work has barely begun on the ruins of Bam's historic citadel, a 2,000-year-old architectural marvel with a big medieval city clustered around it.
The whole enormous site has been reduced to a sea of dust and rubble. Nobody knows how many people may lie buried here, our correspondent says.
Friday's quake had a magnitude of at least 6.3, according to Iranian sources. The US Geological Survey measured it at 6.7.
Bam - about 1,000 kilometres (620 miles) south-east of Tehran - was on the Unesco's list of World Heritage Sites.
Iran suffers frequent earthquakes, with small tremors happening almost daily. In one earthquake in 1990, around 40,000 people died.