President Xi Jinping sent his condolences to Turkish and Syrian leaders on Monday after the most powerful earthquake in nearly a century hit their countries, killing more than 1,400 people.

Xi told Turkish President Recep Tayyip Erdogan and Syrian President Bashar al-Assad in separate messages that he was "shocked" to learn of the disaster, state broadcaster CCTV reported.

He also conveyed "deep condolences for the dead and sincere sympathy for their families as well as for the injured", it said.

The 7.8-magnitude night-time tremor wiped out entire sections of major Turkish cities in a region filled with millions of people who have fled the civil war in Syria and other conflicts.

The initial quake was followed by more than 50 aftershocks, including a 7.5-magnitude tremor that jolted the region in the middle of search-and-rescue work on Monday afternoon.

"I am shocked to learn of the strong earthquake that took place in your countries, causing heavy casualties and loss of property," Xi said in his messages, according to CCTV.

China's official foreign aid agency said it was in communication with Turkish and Syrian authorities and "willing to provide emergency humanitarian aid in accordance with the needs of the affected population". (AFP)