A 7.8 magnitude earthquake hit Turkey and Syria early on Monday; killing hundreds of people and destroying buildings. The shock was felt as far away as the Mediterranean island of Cyprus.
The most powerful earthquake to hit the region in at least a century destroyed entire sections of major cities, killings hundreds and leaving thousands injured. The affected region has been home to millions of refugees fleeing the war in Syria.
The head of Syria's National Earthquake Centre, Raed Ahmed, described the shock as "historically, the biggest earthquake recorded in the history of the centre".
At least 245 people died in government-controlled parts of Syria, and in northern areas held by pro-Turkish factions, according to the health ministry and a local hospital.
At least 284 people died in Turkey, Vice President Fuat Oktay said on Monday, adding that more than 2,300 people had been injured and that search and rescue work was continuing in several major cities.
The rescue effort was being hampered by a winter blizzard that had covered major roads in ice and snow.
Too early to give a death toll
The US Geological Survey said the quake struck at 04:17 am local time (0117 GMT) at a depth of about 17.9 kilometres near the Turkish city of Gaziantep, which is home to around two million people.
Turkey's AFAD emergencies service centre put the first quake's magnitude at 7.4, adding that it was followed by more than 40 aftershocks.
Turkish President Recep Tayyip Erdogan conveyed his sympathies and urged national unity.
"We hope that we will get through this disaster together as soon as possible and with the least damage," the Turkish leader tweeted.
US National Security Advisor Jake Sullivan said Washington was "profoundly concerned".
"We stand ready to provide any and all needed assistance," Sullivan said.
The earthquake struck a predominantly Kurdish area of Turkey near the border with Syria.
The governor of the city of Kahramanmaras said it was too early to estimate the death toll because so many buildings had been destroyed, leaving people trapped inside.
"It is not possible to give the number of dead and injured at the moment because so many buildings have been destroyed," the governor said. "The damage is serious."
Dozens dead in rebel-held Syria
Dozens of people were killed and hundreds injured in rebel-held areas of Syria.
The earthquake left northwestern Syria "in a state of catastrophe" with "destruction, devastation, and collapse of buildings," the White Helmets rescue group said on Twitter.
"Hundreds of injuries, dozens of deaths, many trapped under the rubble or stranded in the winter cold," the group which operates in rebel-held parts of the country said, without providing a specific number.
A doctor at a hospital in the northwestern province of Idlib said it had received the bodies of 30 people.