A powerful earthquake has struck in south-eastern Turkey, near the Syrian border, killing hundreds of people as they slept and trapping many others, reports BBC.
The US Geological Survey said the 7.8 magnitude tremor struck at 04:17 local time (01:17 GMT) at a depth of 17.9km (11 miles) near the city of Gaziantep.
Turkey's Vice-President Fuat Oktay said the death toll there had risen to 284.
In Syria, more than 380 people died, with victims in both government-controlled and rebel-held areas.
The Syrian health ministry said 239 people had died in the provinces of Aleppo, Latakia, Hama and Tartus.
The White Helmets rescue group, which operates in rebel-controlled areas of north-western Syria, said on Twitter that at least 147 people had died there.
There are fears the number of deaths will rise sharply in the coming hours.
Many buildings have collapsed and rescue teams have been deployed to search for survivors under huge piles of rubble.
The epicentre of the quake was in the Pazarcik district of Kahramanmaras province. Turkish Interior Minister Suleymon Soylu said 10 cities were affected: Gaziantep, Kahramanmaras, Hatay, Osmaniye, Adiyaman, Malatya, Sanliurfa, Adana, Diyarbakir and Kilis.
In Gaziantep, at least 80 people were killed, officials said, while 70 died in Kahramanmaras.
In Malatya province, north-east of Gaziantep, at least 47 people were killed. In Sanliurfa, to the east, there were 18 deaths. Other deaths were reported in various places including Diyarbakir and Osmaniye.
Read more: Death toll from earthquake in Turkey, Syria rises to over 600
At least 2,323 people were injured in Turkey and nearly 1,000 in Syria.
A BBC Turkish correspondent in Diyarbakir reported that a shopping mall in the city collapsed.
The tremor was also felt in Lebanon and Cyprus.
"I was writing something and just all of a sudden the entire building started shaking and yes I didn't really know what to feel," Mohamad El Chamaa, a student in the Lebanese capital, Beirut, told the BBC.
"I was right next to the window so I was just scared that they might shatter. It went on for four-five minutes and it was pretty horrific. It was mind-blowing," he said.
Rushdi Abualouf, a BBC producer in the Gaza Strip, said there was about 45 seconds of shaking in the house he was staying in.
Turkish seismologists estimated the strength of the quake to be 7.4 magnitude. They said that a second tremor hit the region just minutes later.
Turkey lies in one of the world's most active earthquake zones.
In 1999, more than 17,000 people were killed after a powerful tremor rocked the north-west of the country.