At least 10 people have died and 57 others were injured after a chain-reaction crash involving seven vehicles on a motorway in north-west Turkey, officials said.

The pile-up occurred in dense fog and low visibility on the Northern Marmara Highway in Sakarya province, some 93 miles from Istanbul.

An investigation has been launched into the accident, but governor Yasar Karadeniz of Sakarya said it likely took place when a vehicle hit a truck in poor visibility, triggering other crashes at the rear.

At least three intercity buses were involved in the incident.

Authorities believe some passengers died when they left their vehicles and were struck by another vehicle, Mr Karadeniz told reporters at the scene.

Seven of the injured were in a serious condition, the governor said.

Police and emergency personnel were seen clearing the wreckage at the scene.