A 7.2 magnitude earthquake hit eastern Turkey, in the province of Van, on the border with Iran.
The quake struck at 13:41, local time, at 17 km (10 miles) north-east Van city.
Van province appeared to be particularly badly hit and officials warning of damage to buildings and infrastructure. Some of the buildings in the area of Van have collapsed and casualties are reported.
According to specialists, Turkey is particularly vulnerable to earthquakes because it sits on major geological fault lines.
In 1999, two earthquakes with a magnitude of more than 7 hit Turkey and killed almost 20,000 people in densely populated parts of the north-west of the country.
TV footages showed damaged buildings and vehicles, and panicked residents spilling out into streets.
According to Anatolia news agency, the rescue workers were searching the wreckage of a seven-storey building in the city of Van for people thought to be trapped in the rubble.
It was also reported that 50 people had been taken to hospital in Van with injuries.
Bekir Kaya, mayor of Van, told NTV television:
“Two buildings collapsed in Van, but the telephone system is jammed due to panic and we can’t assess the entire damage immediately.”
Zulfikar Arapoglu, mayor of Ercis, another town in Van province, told NTV: “There are so many dead. Several buildings have collapsed, there is too much destruction.”
“We need urgent aid, we need medics,” Zulfikar Arapoglu is reported by the Associated Press as saying.
The US Geological Survey (USGS) originally gave the magnitude as 7.3 but later corrected it to 7.2.
But Turkey’s Kandilli observatory gave it a preliminary magnitude of 6.6.
The USGS has revised the depth of the quake from 7.2 km (4.5 miles) to 20 km (12.4 miles), which is still relatively shallow and has the potential to cause damage.
Prime Minister Tayyip Erdogan was reportedly heading to Van to see the damage.