An attack on a police headquarters in northern Iraq has killed at least 30 people and wounded 70, officials say. 

Gunmen stormed the headquarters in the city of Kirkuk after a car bomb was detonated by a suicide attacker on Sunday, police said.

Witnesses said the vehicle that was detonated was painted to appear as though it was a police car, and the fighters who sought to seize the compound were dressed as policemen.

Natah Mohammed Sabr, the head of the city's emergency services department, said the attackers were armed with guns, grenades and suicide vests and were trying to force their way into the police headquarters after the turmoil caused by the car bomb. 

He said the explosion damaged nearby buildings. 

Al Jazeera's Jane Arraf, reporting from Baghdad, said she was receiving "conflicting reports on what exactly happened in the attack".

"This attack took place in the directorate of police, which is in a crowded area, lots of markets around. Civilians as well as police are thought to be among the dead," she said. 

"[The attack] bear a hallmark of an al-Qaeda style attack with the type of explosives used and the coordination," she added citing officials. 

No group immediately claimed responsibility for the attack. 

Kirkuk, an ethnically mixed city of Arabs, Kurds and Turkman, is at the centre of a dispute over oil and land rights between Baghdad's central government and the autonomous Kurdistan enclave in the north.

Source: Al Jazeera and agencies