The sheer scale of devastation caused by the earthquake and its aftershocks can be seen in photos and videos on social media posted by people in Turkey and Syria. Eyewitnesses also spoke of what happened. BBC News collects and verifies the information.

 The tremor of the main earthquake - which occurred at 04:17 local time - was felt more than a hundred miles in each direction from the epicenter - across southern Turkey and northern Syria.

 Witnesses described being shaken out of their sleep and running to their cars for safety from the damaged buildings.

 “I have never felt anything like this in the 40 years I have lived,” said Erdem, who lives in Gaziantep. "We were rocked at least three times very vigorously, like a baby in a crib

 "I barely got myself and my family out of the building. We were just emerging from the wreckage when we saw someone put his hand through a small gap. The building collapsed on our friend who tried to save them. They have no chance of escaping. It completely collapsed on them. We are in a very difficult situation."

 Videos have emerged showing large fires in southern Turkey, with people claiming the earthquake caused gas pipelines to explode, burn, and spiral out of control.

 Russell Pegram of Gaziantep, Essex, described efforts to help elderly neighbors escape from apartment buildings in frigid temperatures.

 "Neighbors got together, it was a team business. If there was an old lady or old man who came down and you had room in your car, everyone would get blankets and share, whatever they could do."

 The earthquake turned the city's citadel and Shirvan mosque into ruins. Gaziantep Castle was one of the best preserved castles in the country dating back to Roman times