The death toll from a powerful earthquake that shook northwestern Turkey early Tuesday surpassed 2,100 this morning, and officials said that figure could climb dramatically as search teams continued to comb through the concrete rubble of scores of apartment buildings.

More than 13,000 people were injured in the quake, which struck at 3 a.m. as most of the region's residents were asleep. Tens of thousands more were left homeless as houses and apartments collapsed. The temblor cut off electricity throughout the area, heavily damaged major roads and bridges and ignited a fire at an oil and gas depot that burned out of control.

The earthquake -- which U.S. scientists measured as high as 7.8 on the open-ended Richter scale of seismic disturbance -- was centered on this industrial city of 500,000 on the Sea of Marmara. The nearby port of Golcuk was said to be the city hit hardest by the quake, but there was also significant damage in Istanbul, 50 miles to the northwest, as well as in the cities of Yalova and Sakarya, where state television said 500 people had been killed.

The quake was felt as far away as Ankara, the capital, 200 miles to the east, and across parts of the Balkan countries to the west.

"There are hundreds of buildings collapsed; we need everything -- field hospitals, kitchens, tents and ambulances," said Nihat Ozgol, the governor of the town of Yalova.

The semi-official Anatolian News Agency, quoting the prime minister's crisis center, set the overall death toll at 2,160 and the number of injured at 13,179 early today.

In Istanbul, most of the damage was confined to the shoddy apartment buildings and shantytowns that ring the city, while such architectural landmarks as the Blue Mosque, Santa Sophia Church and Topkapi Palace were said to have weathered the quake unscathed.

Turkish authorities said the magnitude of the temblor -- the most powerful ever in the earthquake-prone Turkish northwest -- overwhelmed their ability to respond effectively. Authorities declared a state of emergency in the disaster zone, which is in the most heavily populated region of the country.

Here in darkened Izmit, construction cranes working by the light of automobile headlights were unable to lift the huge concrete slabs that crashed onto hundreds of apartment dwellers. Many local residents were reduced to pounding with small mallets on the toppled stonework in a fevered attempt to free their relatives.

Balls of orange flames billowed hundreds of feet high in a thick cloud of oily smoke above the damaged refinery in Izmit, the largest in the country. The plant manager said the blaze was out of control, and officials ordered the area surrounding it evacuated.

Highways were jammed all day Tuesday with motorists seeking to flee what they feared could be a series of damaging aftershocks; at least 300 lesser tremors were counted during the day. Many people in Istanbul and other nearby cities and towns heeded broadcast warnings and camped outdoors overnight beneath makeshift shelters covered with bed sheets.

Prime Minister Bulent Ecevit said the quake was the most devastating natural disaster he had ever seen and predicted a lengthy rebuilding effort. "There is no water, there is no food, there is no electricity, so many people are still under the rubble," said Ecevit, who toured some of the most heavily damaged areas before convening an emergency cabinet meeting. "The loss is huge. . . . May Allah help our state and people."

U.S. Energy Secretary Bill Richardson, who was visiting Istanbul at when the quake hit, told reporters that the shaking lasted for 45 seconds. He agreed with Ecevit that Turkey will need a long time to recover.

The Turkish army dispatched aid convoys, and the Red Crescent Society flew in thousands of tents, but local officials pleaded for search and rescue teams and equipment capable of moving the heavy debris.

President Clinton sent a military search team and said that "on behalf of all Americans, our thoughts and prayers are with the victims and their families. . . . Turkey has been our friend and our ally for a long time now. We must stand with them and do whatever we can to help them get through this terrible crisis." Similar pledges were made by Germany, Britain, France, Switzerland, Israel and even Greece, Turkey's longtime regional rival.

On the outskirts of Istanbul, officials reported that the low-income area of Avcilar and the suburbs of Halkale and Kocatepe were hard hit and that a substantial number of residents in these neighborhoods were missing.

In Golcuk, residents complained to reporters that local officials had provided little help in freeing those trapped under the rubble. Scores of naval officers at a collapsed barracks there were among those rescuers were attempting to reach. Officials said they feared that as many as 160 people had died in the barracks; at least 20 bodies were pulled from the debris on Tuesday. Ecevit reported that senior navy officials who had attended a ceremony on Monday were among those in the barracks at the time of the quake.

The damage in many urban centers appeared almost random, with many buildings remaining intact while others nearby were destroyed. Some residents said bad construction practices were to blame, while others attributed the devastation to bad luck. But the result was that many urban streets were turned into dead ends, blocked by downed power lines or large piles of compacted debris.

Verdat Filiz, a 36-year gas station attendant, said he was on the night shift when the quake hit Izmit, and was not in his fifth-floor apartment when it collapsed onto the first floor. A similar six-story building next door was unscathed. His wife, who had been sleeping, escaped without serious injury, but his sister, Mahmure, and her two daughters who lived on the second floor were still missing late Tuesday and presumed buried in the rubble.

Izmit's hospital was deluged with hundreds of injured people, including many whose bones were shattered when the floors above their apartments collapsed, carrying them along in a swift plunge to the ground, according to Kamil Erkan, a doctor of internal medicine.

Bilgi Fidan, 25, lay on a foam mattress next to dozens of others and recounted how "the ceiling fell over me" with a loud crash a few minutes after 3 a.m. "I was full of luck," she said, explaining why she survived while both her parents remain trapped under the rubble.

Residents fled the Izmit area partly because electrical power had been cut off and most shopkeepers closed their stores out of fear of aftershocks, leaving the city with few sources of food. Neighborhoods surrounding the oil depot, owned by the state-controlled company Tupras, were evacuated as the fire there intensified, while many others living above the company's pipelines said they worried that the explosions in the port would threaten their dwellings.

The resulting jam of cars and trucks on nearby highways further hampered rescue efforts; some ambulances took 20 minutes to travel a mile.

The earthquake occurred along the North Anatolian fault line. Quakes such as Tuesday's mark the instantaneous release of geologic stress that has built up as two tectonic plates slide slowly past each other. The plate on which Turkey is located, according to some scientists, is moving westward at a rate of 0.1 inch a year.

Turkey has been hit by several major earthquakes in this decade. In March 1992, more than 500 people were killed when a quake hit eastern Turkey. In October 1995, 73 people were killed in a temblor in southwestern Turkey. And on June 27, 1998, a 6.3-magnitude quake hit the southern city of Adana, killing 144.