Survivors - many with relatives still entombed - watched helplessly as the operation started in some locations. There are few people in the disaster zone who have not lost at least one member of their family.

The BBC's James Coomarasamy: "These people will be refugees in their own country"

Turkish officials say they are convinced that the need to clear up quickly to prevent the risk of disease outweighs the remote hope that a painstaking search of each building might yield more survivors.

Their dilemma was highlighted on Monday, when a four-year-old boy was found alive in the wreckage of a building in Cinarcik, 35 miles south of Istanbul.

Rain adds to problems

He was pulled out by Israeli army rescuers and taken to hospital in Istanbul for treatment.

"He is in good condition. He asked for water and told us he is hungry," said Dr. Yusuf Bahadir.

A few rescue teams have still not given up hope

The problems facing the authorities were exacerbated when heavy rain broke out.

That will make the wreckage heavier and increase the risk that it could shift and topple on to rescuers.

It will also make life even more miserable for the thousands of survivors living in makeshift shelters.

Health officials, already fearful of the onset of diseases such as typhoid and dysentry, say the rain could be a mixed blessing.

On the one hand, it could wash away the dirt and dust that might carry sickness. But if it turns warm again, there could be an increased risk of disease from mosquitos and flies.

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

The BBC's Peter Biles in Adapazari: "The task of demolition seems hopeless"

More than 115,000 buildings collapsed, many of them multi-storeyed apartment blocks, home to dozens of families.

The number of dead has officially been put at 12,000 although officials say more than 30,000 other bodies may still be buried in the rubble.

Some bodies are being buried quickly in mass graves with photographs taken to assist relatives with identification at a later date.

But the effort is now being concentrated on looking after the survivors, many living in tent cities, often with no water supplies.

The USS Kearsarge has arrived to offer medical help

As some of the foreign rescue teams left for home, two US warships from the Sixth Fleet - USS Kearsarge and USS Gunston Hall - arrived in the Sea of Marmara off Izmit. Another ship is on its way.

As well as bringing 2,100 troops, the warships are equipped with four operating rooms, 17 intensive care beds and 84 medical personnel.

President Suleyman Demirel has pledged to take steps to improve construction laws, seismic monitoring and earthquake response.

Confident of recovery

"The ground beneath us is rotten. Yet we have no choice but to live on it," he said. "What we have to do is be more careful."

The BBC's Robin Aitken reports on the legacy of the earthquake

He added that he was confident the country would rebuild itself. "Turkey will not remain under this shock," he said. "It has not overcome it yet, but it will overcome it."

Poor building methods are being blamed for compounding the number of casualties. Many survivors have accused the government and military of acting too slowly and without coordination after the earthquake.

The government is considering issuing special earthquake bonds to help fund reconstruction after the quake which struck the heart of Turkey's main industrial area.

The final bill for rebuilding the region's infrastructure is expected to run into billions of dollars.

Read the accounts of those who experienced the earthquake by clicking here