The crash involved seven vehicles, including three buses and a truck on the North Marmara highway near the Dagdibi neighbourhood of Sakarya province, according to the state-owned Anadolu news agency.

The cause of the accident has not yet been determined, Anadolu said.

Private news channel NTV said the area was covered with heavy fog and visibility was low.

The governor of Sakarya province told local media that 57 people were injured and taken to hospital.