Paul Adams reports from the earthquake's epicentre - Izmit : "So far nothing seems to be working"

Latest government figures say nearly 3,500 people are confirmed dead, and more than 16,000 injured.

Hot weather has led to fears that people trapped in the rubble of collapsed buildings will die of dehydration or suffocation before rescuers can reach them.

Foreign assistance has begun to arrive in the form of expert rescue teams, armed with the special equipment needed to detect the presence of living people under the rubble.

Jonathan Beale: "The chances of people surviving get slimmer by the hour"

The quake has been assessed at having measured 7.4 on the Richter scale - higher than originally thought.

Aftershocks measuring up to five on the Richter scale have been felt during Wednesday morning - more than 24 hours after the initial shock.

Foreign support

Israel, Japan, Germany, the United States, Britain and Russia are sending groups of experts in search and rescue, and sniffer dogs.

They are bringing with them equipment sensitive to heat and to carbon dioxide - both signs of living people trapped beneath the rubble.

Even Turkey's traditional rival Greece has offered to send specialist personnel and hospital equipment.

Makeshift medical centres have been set up on street corners and in ruined buildings.

Turkish emergency workers and ordinary citizens - many using their bare hands - worked throughout the night, searching for survivors.

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

Widespread devastation

The fire at the oil refinery could spread further

The quake, thought to be one of the most powerful this century, struck a densely populated area of the country.

There is widespread destruction, from Istanbul to the port of Golcuk about 130km (80 miles) to the south-east.

The most serious damage was in Izmit, the city closest to the epicentre of the earthquake, where 800 people are known to have died.

Among the damaged buildings is a hospital, where patients and medical staff are trapped and feared dead.

Chemical blaze

Also in Izmit, the quake has caused a massive fire at Turkey's largest oil refinery.

The governor of the the region, Memduh Oguz, said there was a danger the blaze might spread and cause a new disaster.

Staff at the refinery and people living nearby have been evacuated. A fertilizer plant containing thousands of tons of ammonia is also threatened by the flames.

The BBC's Rageh Omaar:"The scale of destruction to the country's infrastructure has been extensive"

Local firemen have been unable to control the blaze, which has engulfed three of the refinery's 30 oil tanks.

French and Israeli teams, with special chemical equipment, have arrived to help, and French and German fire-fighting planes, used to put out oil-well fires in Kuwait during the Gulf War, are on their way.

Naval base destroyed

In Golcuk, at least 200 people are missing in the ruins of a naval base destroyed by the quake.

They include senior naval officers who had assembled for a meeting at the base.

Throughout the region, tens of thousands of survivors, including many whose homes were not destroyed, spent Tuesday night sleeping outside, afraid of the danger posed by aftershocks.

Compensation promise

Seven affected provinces have been declared a disaster zone, enabling the government to commandeer all private and public facilities for the relief effort.

The government has also promised compensation to victims of the quake.

But already many residents are beginning to express anger at the poor construction methods and lax safety standards that produced buildings unable to withstand such a tremor in a known earthquake zone.

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