A powerful earthquake with a magnitude of 6.6 shook southeastern Turkey on Sunday, Turkey's Kandilli Observatory said, triggering the collapse of buildings and killing many people, according to a local mayor.

State-run media reported 50 people had been injured, while the prime minister's office said the earthquake had caused a loss of life and damage. No figures were available on the death toll.

'A lot of buildings collapsed, many people killed, but we don't know the number. We are waiting for emergency help, its very urgent,' Zulfukar Arapoglu, the mayor of Ercis district, which was hit badly, told the news broadcaster NTV.

'We need tents urgently and rescue teams. We don't have any ambulances, and we only have one hospital. We have many killed and injured,' he said.

Emergency teams were trying to rescue people believed to be trapped in a building in Van, near the Iranian border, state-run news agency Anatolian said. It said 50 injured people had been taken to hospital in Van, but did not give details on how serious their injuries were.

The Kandilli Observatory said the earthquake struck at 1041 GMT and was 5 km deep. The U.S. Geological Survey earlier reported that the magnitude was 7.6.

Television pictures showed damaged buildings and vehicles, crushed under falling masonry, and panicked residents wandering in the streets.

Turkish media said phone lines and electricity had been cut off. Prime Minister Tayyip Erdogan was heading to Van to see the damage, media reported.

Aftershocks continued after the initial quake, whose epicentre was at the village of Tabanli, north of Van city, the agency said.

In Hakkari, a town around 100 km south of the city of Van in southeastern Turkey, a building could be felt swaying for around 10 seconds during the quake.

There was no immediate sign of any casualties or damage in Hakkari, around two and half hours drive through the mountains from Van, around 20 km from the epicentre.

Major geological faultlines cross Turkey and small earthquakes are a near daily occurrence. Two large quakes in 1999 killed more than 20,000 people in northwest Turkey.

Two people were killed and 79 injured in May when an earthquake shook Simav in northwest Turkey.-Reuters