In PHOTOS: Devastating 7.3 earthquake flattens east Turkey

A 7.3 magnitude earthquake in eastern Turkey today has killed 500 to 1,000 people, the head of a seismological institute in Istanbul said.

"Five hundred to 1,000 people are estimated to have been killed in the quake," Professor Mustafa Erdik, director of the Kandilli seismological institute in Istanbul, told a news conference.

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The powerful quake, the strongest to hit the country in years, and its aftershocks struck Van, a large eastern city populated mainly by Kurds.

Hundreds are feared trapped under the rubble of collapsed buildings and officials warned they were struggling to assess the extent of the damage.At least 50 people were taken to hospital in Van, Anatolia news agency said.

Many of the buildings destroyed were blocks of flats. Aftershocks rattled the region. Local officials have appealed for tents and supplies to look after those made homeless by the disaster, reported the BBC.

"There is serious human and material loss," said a brief statement from the the national disaster body which is based in the prime minister's office.

"Many multi-floor buildings, hotels and a dormitory were collapsed," said Veysel Keser, a local official from Van. "We can hear voices from the collapsed buildings," he said.

Television footage showed collapsed buildings and vehicles, with residents rushing in panic in the streets. "People are panicked. The telecommunication services have collapsed. We cannot reach anybody," Van Mayor Bekir Kaya told the NTV television in an initial assessment.

The government is due to send satellite phones to the region, according to media reports. The army will also send search and rescue teams to the area.

Turkey Prime Minister Recep Tayyip Erdogan has cancelled his official programme and will fly to the area Sunday afternoon, the CNN reported.

Israel offered Turkey "any help if may require" after the earthquake, Israel Defence Minister Ehud Barak's office said.

Turkey sits on major geological fault lines, making it vulnerable to earthquakes. The United States Geological Survey measured the quake at 7.3 magnitude and said that an aftershock was of 5.6 magnitude had also been registered. The epicentre of the aftershock, which occurred at 1056 GMT, was located 19 kilometers northeast of Van, the institute added.

The quake was also felt over the border in northwest Iran, causing some panic in major cities, Iranian media reported, but without any mention of casualties or damage.