Istanbul and at least seven other cities were hit at 3am local time (1am BST). Most of the dead were crushed in their sleep as the force of the earthquake destroyed apartment blocks across Turkey's industrial heartland. Through the terrible dawn, and all day long, rescuers dug in the rubble of shattered buildings with everything from bare hands to picks and shovels.
In the town of Golcuk, 55 miles south-east of Istanbul, the mayor said 500 buildings housing 20,000 families had collapsed. "There could be 10,000 people under the debris," Ismail Baris said. The Golcuk dead included 160 sailors who perished in the collapse of two navy buildings,while hundreds died in nearby Izmit, the epicentre of the earthquake.
A fire which broke out at Turkey's biggest oil refinery was blazing out of control, the general manager Husamettin Danis said. Fears of an explosion forced the evacuation of the plant, in Izmit, which is operated by the state-owned petroleum company Tupras.
Turkish television said 500 people were killed in Adapazari, 90 miles east of Istanbul, while in Yalova, south of Golcuk, the governor, Nihat Ozgol, said 250 bodies had been recovered.
Another 116 people were killed in Istanbul, and hundreds more were injured there by falling masonry or when they jumped from balconies.
Layer by layer, from thousands of sites around western Turkey, through the day and into last night, the ruins gave up the dead. Many were clothed in the pyjamas and nightgowns they wore when the immense quake struck with 45 seconds of destruction. Some of the bodies were shrouded in blankets and sheets.
But there was hope among the ruins. In a town outside Istanbul, rescuers searching for children they knew to be buried in the rubble of their homes broke into excited applause as a five-year-old boy was hoisted from the debris and on to the shoulders of his smiling father.
When the quake struck Muzzafer Yarla was seeking some respite from the hot August night on the balcony of his Istanbul flat. The seven-storey building collapsed beneath him like a house of cards. Mr Yarla was hurled into the street, somehow surviving. But yesterday his only thoughts were for his family, buried in the rubble of his home. "Tell me my children are alive," he pleaded from his stretcher. But moments later rescue workers stumbled across a child's bare feet, clearly lifeless, sticking through the rubble. There was a hush as neighbours identified the corpse, then they struck up a wail of grief.
Hamza Bikbay and his wife, Sema, were dragged alive from the rubble of their home in Golcuk. "Everything started collapsing," said Mr Bikbay. "We held hands and I said, `OK, we're dying'."
There were no immediate reports of damage to Istanbul's architectural treasures such as the Blue Mosque, though the quake toppled the minarets of dozens of mosques in the region. The Strait of Bosporus remained open to two-way traffic and air officials said both Ankara and Istanbul airports were operating normally.
The effects of the quake, which was felt 275 miles away in Ankara, were curiously random. It turned sturdy looking apartment blocks into concertinas of twisted concrete and metal, while identical structures next door stood seemingly unharmed. Collapsed buildings blocked roads, slowing rescue efforts that were further hampered by traffic jams caused by residents fleeing cities, while others tried to get into them for news of loved ones.
Electricity pylons were ripped out and power cables torn apart, leaving the region without electricity. Still the toll mounted."This is as much as we have room for and they keep coming in," said Saban, an Izmit caretaker who surveyed the 20 fresh graves workmen had dug under a burning sun. A trail of mini-buses and cars carrying the dead wound its way up a nearby hilltop. There, workmen operating bulldozers dug rows of trenches to take the overflow. "The bulldozers will keep digging until we have room for everyone," said Veysel Cakir, overseeing the grim operation. Islamic tradition says the dead should be buried within 24 hours. Outside a hospital, 150 doctors and nurses struggled to save the wounded strewn among the dead.
The authorities had criticised builders for failing to protect homes against tremors after more than 140 people died in southern Turkey last year in an earthquake measuring 6.3 on the Richter scale. Yesterday's measured 7.
The Prime Minister, Bulent Ecevit, called the quake the worst natural disaster he had ever seen and said it would require gargantuan efforts to rebuild. "The loss is huge," the 73-year-old premier said in a trembling voice. "It is the biggest natural disaster I have witnessed... May Allah help our state and our people."
The International Federation of Red Cross and Red Crescent Societies appealed for $7m to help the estimated 100,000 victims. A spokesman, Helge Kvam, said tents, blankets, food and water purification tablets would be the top priority.
Britain's Deputy Prime Minister, John Prescott, said he was "shocked and saddened" by news of the earthquake, and Tony Blair sent a message of sympathy to his Turkish counterpart.
The Foreign Office said that two Britons had been injured by the quake or its aftershocks. It warned against travel to affected areas, saying there could be more tremors.
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