Up to 25 people were killed and some 70 others wounded when a bomb and a car bomb exploded coordinately in Iraq's northern city of Kirkuk on Thursday, a local police source told Xinhua.

"Our latest report said that 25 people were killed and some 70 wounded by the double blasts in Kirkuk," the source said on condition of anonymity.

The attack took place in the morning rush hours when a sticky bomb attached to a car detonated at a parking lot in front of a police headquarters in central the city of Kirkuk, some 250 km north of Baghdad, the source said.

Afterwards, a booby-trapped car parked at the scene went off as Iraqi security forces and dozens of onlookers gathered at the site of the first blast, the source added.

The powerful car bomb explosion destroyed parts of the police headquarters, the source said, adding that many of the killed and wounded were policemen.

"Five of the killed were police officers, including Major Ibraim Hazim, the secretary of the Kirkuk's police chief," the source said.

Earlier, the source put the toll at 12 killed and 50 wounded by the blasts.

The oil-rich Kirkuk province and its capital Kirkuk City are part of disputed areas between the Kurds and both Arabs and Turkomans. The area has long been the hotbed of insurgency since the U.S.-led invasion in 2003.