ANKARA, Feb 7 (AFP) - A major earthquake struck Turkey and Syria on Monday, killing more than 3,800 people and flattening thousands of buildings as rescuers dug with bare hands for survivors.

Dozens of nations pledged aid after the 7.8-magnitude quake, which hit as people were still sleeping and amid freezing weather that has hampered emergency efforts.

Multi-storey apartment buildings full of residents were among the 5,606 structures reduced to rubble in Turkey, while Syria announced dozens of collapses, as well as damage to archaeological sites in Aleppo.

"That was the first time we have ever experienced anything like that," said Melisa Salman, a 23-year-old reporter in the southeastern Turkish city of Kahramanmaras.

"We thought it was the apocalypse."

The head of Syria's National Earthquake Centre, Raed Ahmed, called it "the biggest earthquake recorded in the history of the centre".

The initial quake was followed by dozens of aftershocks, including a 7.5-magnitude tremor that jolted the region in the middle of search and rescue work on Monday.

"We managed to save three people, but two were dead," said Halis Aktemur, 35, in Turkey's southeastern city of Diyarbakir after the quake that was felt as far away as Greenland.

In the southeastern Turkish city of Sanliurfa, rescuers were working into the night to try and pull survivors from the wreckage of a seven-storey building that had collapsed.

"There is a family I know under the rubble," said 20-year-old Syrian student Omer El Cuneyd.

"Until 11:00 am or noon, my friend was still answering the phone. But she no longer answers. She is down there."

Despite temperatures falling below zero, frightened residents in the city were preparing to spend the night on the streets, huddling around fires for warmth.

Nearby, Mustafa Koyuncu was sitting packed inside his stationary car with his wife and their five children, scared to move.

"We are waiting here because we can't go home," the 55-year-old told AFP. "Everyone is afraid."

At least 1,444 people died Monday across Syria, the government and rescuers said.

The new toll brings the total deaths in both countries to at least 3,823 after Turkey revised its toll earlier to 2,379.

Nearly 14,500 people were injured and 4,900 buildings flattened, Ankara announced late Monday.

Turkey declared seven days of mourning for the dead.

The rescue was being hampered by a winter blizzard that covered major roads in ice and snow. Officials said the quake made three major airports in the area inoperable, further complicating deliveries of vital aid.

Monday's first earthquake struck at 4:17am (0117 GMT) at a depth of about 18 kilometres (11 miles) near the Turkish city of Gaziantep, which is home to around two million people, the US Geological Survey said.

Denmark's geological institute said tremors reached the east coast of Greenland about eight minutes after the main quake struck Turkey.

More than 12,000 people are injured in Turkey, the disaster management agency said, while Syria said at least 3,411 people were injured.