BAGHDAD, July 18 (Xinhua) -- Eight people were wounded Wednesday in the ethnically mixed city of Kirkuk in five explosions in central the city, a local police source said.

The blasts occurred at night when unidentified gunmen threw hand grenades randomly on civilian cars moving at a main street in the city of Kirkuk, Lt. Gen. Salih al-Jubouri from the Salahudin police command told Xinhua.

The blasts damaged several cars and wounded eight people aboard, Jubouri said.

Iraqi security forces intensified security measures and launched investigation into the attacks as part of their efforts to hunt down the attackers, Jubouri added.

Kirkuk, some 250 km north of the Iraqi capital Baghdad, is part of the disputed areas claimed by both Iraqi central government and the semi-autonomous region of Kurdistan.

In October, the Iraqi federal security forces took control of Kirkuk province, including its oil fields and military bases, after the withdrawal of the Kurdish Peshmerga forces.

Since then, the city witnessed attacks by gunmen against the Iraqi forces and civilians from time to time, while the western and southern part of the oil-rich Kirkuk province have witnessed attacks by remnants of Islamic State militants.