At least 119 people perished in government-controlled portions of Syria.
Images on television showed stunned citizens in Turkey.
The earthquake was one of the most powerful to strike the region in at least a century.
A 7.8-magnitude earthquake struck Turkey and Syria early Monday, killing about 200 people, leveling buildings while many others were still sleeping, and spreading shocks as far away as Cyprus and Egypt.
According to the health ministry and a local hospital, at least 119 people perished in government-controlled portions of Syria, as well as in northern areas held by pro-Turkish forces.
Images on television showed stunned citizens in Turkey standing in the snow in their pajamas, watching rescuers rummage through the debris of destroyed homes.
The quake occurred at 04:17 a.m. local time (0117 GMT) at a depth of around 17.9 kilometers (11 miles) in the Turkish city of Gaziantep, which has a population of about two million people, according to the US Geological Survey.
Turkey’s AFAD emergencies service center put the first quake’s magnitude at 7.4, adding that it was followed by more than 40 aftershocks.
The earthquake was one of the most powerful to strike the region in at least a century, impacting southeastern Turkey, which is home to millions of refugees fleeing Syria and other war-torn countries.
Turkish President Recep Tayyip Erdogan, who will be under enormous pressure to oversee an effective reaction to the accident as the country prepares for a closely contested election on May 14, expressed his sympathies and advocated national togetherness.
“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.
‘People under rubble’
The earthquake struck a restive, primarily Kurdish region of Turkey bordering Syria, a country racked by more than a decade of turmoil that has killed hundreds of thousands and displaced millions.
Rescuers were seen sifting through the wreckage of leveled buildings in Kahramanmaras and neighboring Gaziantep, where huge portions of cities had been demolished, according to images shown on Turkish media.
In one shot from Kahramanmaras, a fire lighted up the night sky, although its origin was unknown.
Buildings collapsed in Adiyaman, Malatya, and Diyarbakir, where reporters watched scared people rush out onto the streets.
Because so many structures were demolished, Kahramanmaras Governor Omer Faruk Coskun said it was too early to estimate the death toll.
“It is not possible to give the number of dead and injured at the moment because so many buildings have been destroyed,” Coskun said. “The damage is serious.”
A historic mosque from the 13th century partially fell in the province of Maltaya, as did a 14-story building with 28 flats.
Rescuers in other locations sounded distraught as they battled to reach survivors buried beneath the debris.
“We hear voices here — and over there, too,” one rescuer was overheard saying on NTV television in front of a flattened building in the city of Diyarbakir.
“There may be 200 people under the rubble.”
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