At least 11 people have been killed by a blast which targeted a police bus in central Istanbul, officials say.
The remote-controlled device was reportedly detonated as the vehicle passed through the busy Vezneciler district at the morning rush hour.
No group has yet said it carried out the attack.
Violence in Turkey has escalated recently as a result of tensions with Kurdish separatists and the conflict in neighbouring Syria.
The explosion happened near the city’s historic Beyazit Square neighbourhood, a major tourist attraction.
At least 36 other people were injured, Istanbul’s governor said.
Pictures showed the wreckage of a bus destroyed and the facade of nearby buildings damaged. Armed police were also seen next to the site.
Reports said gunfire was heard in the area after the blast.