More than 10,000 people are already known to have died and the Turkish authorities are predicting thousands more bodies will be found beneath the rubble.

Sergio Piazzi, a senior United Nations official, says the Turkish authorities believe that about 35,000 people - alive or dead - are still buried under the rubble. Another 45,000 people have been injured.

However Mr Piazzi, of the UN's office for humanitarian affairs, said some hope remained of locating survivors.

"Our experience with the search and rescue phase is that there is a possibility of finding people alive until next Monday or Tuesday," he said.

The BBC's George Eykyn: "They are torn between grief and anger"

Concern is growing for the health of those who have lived through the quake, with disease the latest threat to survivors.

The fear of aftershocks has persuaded millions of people to camp out in the open - close to the decomposing bodies of those killed in the earthquake.

"Perhaps the greatest problem now facing us is that of epidemic," Prime Minister Bulent Ecevit told reporters.

Most rescue workers are wearing masks, and are being immunised against typhoid. Reports are already emerging of cholera cases in some areas south-east of Istanbul.

International doctors treating the injured say the area is ripe for infection.

"There is a problem with sanitary conditions and no running water, dead bodies and heat," said Israeli medic Colonel Giora Martentanozits, part of a flying doctor team in Adapazari.

(Click here to see a map of where the earthquake struck)

Teams are working to chlorinate water, disinfect areas and put recovered corpses in bags before disease starts to spread.

An American team prepares to get to work

Dysentery, diarrhoea and gastroenteritis were starting to strike, said French volunteer Dr Wolff Pierre.

Some estimates put the number of people sleeping outside on Thursday night as high as two million.

The figure included not only those survivors who have lost their homes, but also the people living in and around Bursa - whose governor, Orhan Tasanlar, warned people to stay outside for the night.

The BBC's Chris Morris reports on the disease and contamination which faces the people of Turkey

Further devastation has been reported after a 20-ft high tidal wave in the Sea of Marmara destroyed large areas of the Degirmendere holiday resort moments after the earthquake on Tuesday.

Mass graves

Around the city of Izmit, each day brings a succession of funerals.

The Muslim practice is to bury the dead within 24 hours if possible - and officials are urging swift burial too, fearing the spread of disease from bodies decomposing in the extreme summer heat.

Gravediggers have been working in shifts, night and day.

The BBC's Gavin Hewitt: "The days of miracle are fading"

Often, the new graves are marked with simple wooden markers, names written in ball-point pen.

In Adapazari, one of the worst affected towns, rescue workers buried 963 people in a mass grave. They took pictures of the dead so that they could later be identified by their families.

Damage assessment

The Turkish Government has begun evaluating the cost of Tuesday's earthquake to the national economy.

A Turkish soldier celebrates finding a living survivor

A national business association, Tusiad, said the quake could cost the struggling economy $40bn.

There has been growing anger that so many buildings fell down because no precautions against earthquakes had been taken.

In recent years, officials have turned a blind eye to contractors who have skimped on materials to provide housing for a flood of rural migrants.

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