A car bomb attack targeting a police bus has killed at least 11 people in central Istanbul, officials say.
The explosives were remotely detonated as the vehicle passed through the busy Vezneciler district at the morning rush hour, reports said.
No group has 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.
Four civilians and seven police officers were among the dead, Istanbul’s governor, Vasip Sahin, said.
Some 36 other people were injured, he added.
Reports said gunfire was heard in the area after the blast.
Turkey has suffered a spate of bombings this year, including two suicide attacks in tourist areas of Istanbul blamed on the co-called Islamic State, and two car bombings in the capital, Ankara, which were claimed by a Kurdish militant group.
The outlawed Kurdistan Workers Party (PKK) claimed responsibility for a 12 May car bomb attack in Istanbul that wounded seven people.
In that attack, a parked car was also blown up as a bus carrying security force personnel passed by.
The PKK, which has waged an armed insurgency against the Turkish state since 1984, frequently targets passing police and military vehicles with remote-controlled car bombs in its attacks in the largely Kurdish southeast.