Turkey's disaster agency said 2300 people died there, while it is estimated that 783 people died in Syria as of this writing.

The numbers are expected to soar as rescuers grapple with mountains of rubble in snowy weather. 

Turkey’s earthquake is considered the country’s worst disaster in almost a century, Turkey’s president Erdogan said. The US Geological Survey said the 7.8 magnitude tremor smashed at 04:17 local time (01:17 GMT) at a depth of 17.9km (11 miles) near the city of Gaziantep.

Seismologists said the first quake was one of the most significant ever recorded in Turkey. Survivors said the shaking continued for two minutes straight. 

Twelve hours following the first earthquake, another struck the Elbistan district of Kahramanmaras province at a 7.5 magnitude. 

An official from Turkey's Disaster and Emergency Management Authority said it was "not an aftershock" and was "independent" from the earlier quake.

Turkey is one of the world's most active earthquake zones. President Recep Tayyip Erdogan said Monday's disaster was the worst the country had seen since 1939 when the Erzincan earthquake in eastern Turkey killed nearly 33,000 people.

However, in 1999 there was another deadly quake that killed more than 17,000 in Turkey's northwest.

One Kahramanmaras resident, Melisa Salman, said living in an earthquake zone meant she was used to "being shaken," but Monday's tremor was "the first time we have ever experienced anything like that."

"We thought it was the apocalypse," she said.

Many thousands of people have been injured - with at least 5,385 people hurt in Turkey and 2,000 in Syria.

Thousands of buildings have crumpled, and several videos show the moment they fell as onlookers ran for cover. Many buildings that were four or five stores high are now flattened, roads have been destroyed, and there are vast mountains of rubble as far as the eye can see.

Among the buildings destroyed was Gaziantep Castle, a historic landmark that existed for more than 2,000 years.

Turkey's energy infrastructure has also been hit, and videos showed large fires in southern Turkey. Social media users claimed they were caused by damage to the gas pipelines.

Turkey's energy minister Fatih Donmez confirmed there had been severe damage to the infrastructure, however, he did not mention the explosions.