ISTANBUL — A rush-hour car bomb targeted a bus carrying riot police in Istanbul on Tuesday, killing 11 people and wounding 36 others, Istanbul’s governor said.

Speaking at the scene of the blast in the Beyazit district, Istanbul Governor Vasip Sahin said the dead included seven police officers and four civilians. At least three of the wounded were in serious condition.

The bomb was placed inside a car and detonated as the police vehicle passed by, Sahin said. There was no immediate claim of responsibility and Sahin would not comment on who may be behind the attack.

Tuesday’s attack was the fourth major bombing in Istanbul this year, with two of them targeting tourists and the others hitting security forces. The spike in violence has led to a sharp dip in tourism, a mainstay of the Turkish economy.

The police bus was flipped over by the force of the blast, which also damaged nearby buildings, including a closed hotel whose entrance appeared gutted and windows were blown out. The blast also shattered windows at a famous 16th-century Ottoman mosque, Sehzadebasi, wrecked several cars and forced the cancellation of some exams at nearby Istanbul University.

President Recep Tayyip Erdogan visited some of the wounded at Istanbul’s Haseki hospital, where two people were undergoing surgery.