Hundreds feared dead and dozens of people injured as quake strikes northeast of the city of Van.
Deaths have been reported after an earthquake with a preliminary magnitude of 7.2 hit eastern Turkey. Turkey's Kandilli Observatory estimated that 500 to 1,000 people could have been killed in Van province.
The seismology institute's estimate was based on the strength of the quake and the structure of the housing in the area. Dozens of people were also injured after several buildings collapsed.
"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.
The Turkish Red Crescent said 25 apartment buildings and one dormitory in Ercis had collapsed.
The quake struck at 10:41 GMT on Sunday, with the village of Tabanli, north of Van city, as its epicentre.
Communications collapsed
At least 50 people were taken to hospital in Van, Anatolia news agency said.
Officials warned that they were struggling to assess the full extent of the damage.
"People are panicked. The telecommunication services have collapsed. We cannot reach anybody," Van Mayor Bekir Kaya told NTV.
The army was to send search and rescue teams to the area.
Aftershocks continued after the initial quake.
The quake was also felt over the border in northwest Iran, causing some panic in major cities, Iranian media reported.
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.