• At least 912 people were killed and more than 5,000 people were injured due to a magnitude-7.8 earthquake that struck central Turkey, President Tayyip Erdogan said on Monday. Erdogan said it was the country's largest disaster since 1939, adding that 2,818 buildings collapsed as a result.

More than 500 people were killed and thousands injured on Monday, after a major earthquake of magnitude 7.8 struck central Turkey and northwest Syria, collapsing buildings and triggering searches for survivors in the rubble.

The quake, which hit in the early darkness of a winter morning, was also felt in Cyprus and Lebanon.

"We were shaken like a cradle. There were nine of us at home. Two sons of mine are still in the rubble, I'm waiting for them,” said a woman with a broken arm and wounds on her face, speaking in an ambulance near the wreckage of a seven-storey block where she had lived in Diyarbakir in southeast Turkey.

"I have never felt anything like it in the 40 years I've lived,” said Erdem, a resident of the Turkish city of Gaziantep, near the quake's epicentre, who declined to give his surname.

"We were shaken at least three times very strongly.”

Turkish Vice President Fuat Oktay said 284 people were killed and 2,323 injured, as authorities scrambled rescue teams and supply aircraft for the affected area, while declaring a ”level 4 alarm” that calls for international assistance.

In Syria, already devastated by more than 11 years of civil war, a government health official said more than 237 people had been killed and about 600 injured, most in the provinces of Hama, Aleppo and Latakia, where numerous buildings tumbled down.

In the Syrian rebel-held northwest, a rescue service said dozens had been killed.

Turkish broadcaster RTR showed rescue workers in Osmaniye province using a blanket to carry an injured man out of a collapsed four-storey building and putting him in an ambulance. He was the fifth to be pulled from the rubble, it said.

Footage on broadcaster CNNTurk showed the historic Gaziantep Castle was severely damaged.

President Tayyip Erdogan spoke by telephone with the governors of eight affected provinces to gather information on the situation and rescue efforts, his office said in a statement.

"There was a huge noise and the building next to ours collapsed when the earthquake happened,” said a 30-year-old in Diyarbakir.

"I rushed outside. There was screaming everywhere. I started pulling rocks away with my hands. We pulled out the injured with friends, but the screaming didn't stop. Then the (rescue) teams came.”

'Totally destroyed'

In the Syrian city of Aleppo, heavily damaged during the war, health director Ziad Hage Taha told Reuters wounded people were“arriving in waves”.

Syrian state television showed footage of rescue teams searching for survivors in heavy rain and sleet.

Rescue workers in rebel-held areas of Syria reported extensive damage.

In the border town of Azaz - an area held by opposition forces - a rescue worker carried a toddler from a damaged building. Another group carried a body wrapped in a white sheet as a crane pulled away concrete slabs, a Reuters witness said.

"Tens of buildings have collapsed in the city of Salqin,” a member of the White Helmets rescue organisation said in a video clip on Twitter, referring to another town about 5 km (3 miles) from the Turkish border.

President Bashar al-Assad was holding an emergency cabinet meeting to review the damage and discuss the next steps, his office said.

People in Damascus, and in the Lebanese cities of Beirut and Tripoli, ran into the street and took to their cars to get away from their buildings in case they collapsed, witnesses said.

US offer of help

The United States was “profoundly concerned” about the quake in Turkey and Syria and was monitoring events closely, White House national security adviser Jake Sullivan said on Twitter.

"I have been in touch with Turkish officials to relay that we stand ready to provide any and all needed assistance,” he said.

The U.S. Geological Survey said the magnitude 7.8 quake struck at a depth of 17.9 km. It reported a series of earthquakes, one of 6.7 magnitude.

The region straddles seismic fault lines.

It was Turkey's most severe quake since 1999, when one of similar magnitude devastated Izmit and the heavily populated eastern Marmara Sea region near Istanbul, killing more than 17,000.

Monday's tremor lasted about a minute and shattered windows, according to a Reuters witness in Diyarbakir, 350 km (218 miles)to the east, where a security official said at least 17 buildings collapsed.

Authorities said 16 structures collapsed in Sanliurfa and 34 in Osmaniye.

Broadcasters TRT and Haberturk showed footage of people picking through building wreckage, moving stretchers and seeking survivors in the city of Kahramanmaras, where it was still dark.

"Our primary job is to carry out the search and rescue work and to do that all our teams are on alert,” Turkish Interior Minister Suleyman Soylu told reporters.

Tremors were also felt in the Turkish capital of Ankara, 460 km (286 miles) northwest of the epicentre, and in Cyprus, where police reported no damage.

"The earthquake struck in a region that we feared. There is serious widespread damage,” Kerem Kinik, the chief of the Turkish Red Crescent relief agency, told Haberturk, issuing an appeal for blood donations.