UPDATE: 3:50 a.m. EDT — Eleven people have been killed and several others injured in an explosion targeting a police bus in central Istanbul, a top Turkish official told the Associated Press. At least 36 people were injured in Tuesday's attack, Gov. Vasip Sahin said, adding that the dead included seven police officials and four civilians.

UPDATE: 3:30 a.m. EDT — At least two people have been killed and several others injured in an explosion targeting a police bus in central Istanbul, Turkish media reported.

Original story:

Several people have been injured after a blast in Istanbul targeted a police bus, Turkish media reported. The attack took place in the central district of Vezneciler.

The bus was carrying police officers in the Beyazit district of Istanbul Tuesday morning, Turkey’s state-run TRT channel reported. The explosion, which occurred near the city's historic Beyazit Square neighborhood, a major tourist attraction, damaged several vehicles and the facade of nearby buildings.

Five people were injured, according to initial findings, the Dogan news agency reported, adding that ambulances and fire engines were dispatched to the scene.

Some local reports also said that the explosion was followed by gunfire. No group has so far claimed responsibility for the attack.