Rescue workers work to save people trapped under debris after an earthquake in Ercis, near the eastern Turkish city of Van, Oct 23, 2011. [Photo/Agencies]

PATNOS, Turkey - Rescue teams on Monday sifted through hills of rubble from flattened multistory buildings trying to reach dozens of people believed trapped after a 7.2-magnitude earthquake struck eastern Turkey. The death toll has so far risen to 279.

Hundreds of rescue teams dug through the night in search of survivors among dozens of pancaked buildings. Residents also searched for their missing as aid groups scrambled to set up tents, field hospitals and kitchens to assist thousands left homeless.

Officials said hundreds of mud-brick homes in villages and concrete buildings in cities tumbled down in the earthquake that struck the province of Van, near the border with Iran, on Sunday.

Worst-hit was the city of Ercis, where about 80 multistory buildings collapsed. Interior Minister Idris Naim Sahin said some 40 buildings in Ercis still had people trapped inside, giving rise to fears that the death toll could increase substantially. The minister did not give any estimates.

Prime Minister Recep Tayyip Erdogan said "close to all" mud-brick homes in surrounding villages had collapsed.

Sahin said 117 were killed in Ercis, another 100 died in Van while some 740 people were injured in the temblor that also rattled parts ofIranandArmenia.

Ercis, an eastern city of 75,000 close to the Iranian border, is in one of Turkey's most earthquake-prone zones. The bustling, larger city of Van, about 55 miles (90 kilometers) south of Ercis, also sustained substantial damage, and highways in the area caved in.

Some inmates escaped a prison in Van after one of its walls collapsed. TRT television said around 150 inmates had fled, but a prison official said the number was much smaller and many later returned.

The quake also damaged some buildings in the town of Patnos, some 30 miles (50 kilometers) northwest of Ercis, where military and Red Crescent trucks were seen transporting tents and other aid equipment.

US scientists recorded more than 100 after shocks in eastern Turkey within 10 hours of the quake, including one with a magnitude of 6.0.

Authorities advised people to stay away from damaged homes, warning they could collapse in the aftershocks.

Many residents spent the night outdoors and lit campfires, while the Red Crescent began setting up tents in a stadium. Others sought shelter with relatives in nearby villages.

Around 1,275 rescue teams from 38 provinces were being sent to the region, officials said, and troops were also assisting search-and-rescue efforts.

Several countries offered Turkey humanitarian aid and assistance with search and rescue efforts but Erdogan said Turkey was able to cope for the time being. Azerbaijan,Iran and Bulgaria nevertheless sent assistance, he said.

Among those offering help were Israel and Greece. The offer from Israel came despite a rift in relations following a 2010 Israeli navy raid on a Gaza-bound aid flotilla that left nine Turks dead. Greece, which has a deep dispute with Turkey over the divided island of Cyprus, also offered to send in a special earthquake rescue team.

Turkey lies in one of the world's most active seismic zones and is crossed by numerous fault lines. In 1999, two earthquakes with a magnitude of more than 7 struck northwestern Turkey, killing about 18,000 people.

More recently, a 6.0-magnitude quake in March 2010 killed 51 people in easternTurkey, while in 2003, a 6.4-magnitude earthquake killed 177 people in the southeastern city of Bingol.

Istanbul, the country's largest city with more than 12 million people, lies in northwestern Turkey near a major fault line. Experts have warned that over crowding and shoddy construction in Istanbul could kill tens of thousands if a major earthquake struck there.