A suicide car bomber joined by other suicide attackers on foot assaulted a provincial police headquarters in a disputed northern Iraqi city on Sunday, killing at least 15 people and wounding 90 others, officials said.

The blast in Kirkuk appeared to be a fresh attack by militants seeking to undermine government efforts in maintaining security nationwide.

A police officer said the car bomber drove his vehicle into the Kirkuk headquarters, followed by suicide attackers on foot armed with machineguns and grenades. He added that police killed all the militants before they could enter the building. He did not say how many attackers there were in total.

The officer spoke on condition of anonymity as he was not authorized to release information. The head of the provincial health directorate, Sidiq Omar Rasool, confirmed the casualty figures.

While there was no immediate claim of responsibility, car bombs and coordinated attacks are favourite tactics for Sunni insurgents such as al-Qaeda's Iraq branch.

The blast damaged the police offices and nearby buildings. Several dead bodies could be seen on the street along with the debris of the car bomb. Police and rescuers dug in the rubble for survivors.

Kirkuk, 290 kilometres north of Baghdad, is home to a mix of Arabs, Kurds and Turkomen, who all have competing claims to the oil-rich area. The Kurds want to incorporate it into their self-ruled region in Iraq's north, but Arabs and Turkomen are opposed.

The city is at the heart of a snaking swath of territory disputed between the Kurds, who have their own armed fighting force, and Iraq's central government.

Al-Qaeda and other insurgent groups are believed to exploit ethnic tensions throughout Iraq's north.