A suicide bomber driving a car and gunmen disguised in police uniforms killed at least 33 people in the Iraqi city Kirkuk on Sunday when they tried to storm the police headquarters.

It was the third major attack in several weeks in or near the northern city, an ethnically mixed area of Arabs, Kurds and Turkmen at the heart of a dispute over oil and land between Baghdad's central government and the autonomous Kurdistan region.

"A suicide bomber driving a car packed with explosives hit the entrance of the headquarters and after the blast gunmen in explosive vests attacked with AK47s and grenades, but the guards killed them," a police official said.

The huge car bomb blast tore into the police directorate's concrete facade, destroyed cars outside, and left bodies under rubble at nearby government offices. Police said there were at least two gunmen.

Several armed groups are active in Kirkuk, and Sunni Islamist insurgents tied to al Qaeda often attack security forces in an attempt to undermine Shi'ite Prime Minister Nuri al-Maliki's government and stoke sectarian tensions.

Last month a suicide bomber disguised as a mourner killed at least 26 at a funeral at a Shi'ite mosque in the nearby city of Tuz Khurmato, and days earlier a suicide bomber driving a truck killed 25 in an attack on a political party headquarters in Kirkuk, 170 km (105 miles) north of the capital Baghdad.

Reuters