A bus crashed into an overpass pillar near Ankara early on Friday killing nine people and injuring 26, Agence France-Presse reported, citing the governor of Ankara.
The accident occurred at 5:00 am (0200 GMT), public broadcaster TRT said. It was on its way from Eskişehir, a city west of Ankara.
Ankara Governor Vasip Şahin said preliminary information suggested the driver had fallen asleep as there was no indication he had tried to brake.
An investigation has been launched.
Bus accidents are relatively common in Turkey.
In May 10 people died and 40 were injured when a bus collided with two cars and a truck on a highway near the southern city of Mersin.