A Turkish military cargo plane carrying at least 20 people has crashed near the Azerbaijan-Georgia border, Turkey's defence ministry has said.

Officials have not confirmed the number of casualties, but Turkish President Recep Tayyip Erdogan earlier offered his condolences to "our martyrs".

Search and rescue efforts have begun at the scene. The number on board included flight crew, officials said.

The defence ministry said the C-130 cargo plane had been travelling from Azerbaijan to Turkey.