Four more people, including two security guards, were wounded in the attack near the office of Patriotic Union of Kurdistan (PUK), the party of Iraqi President Jalal Talabani.

"The bombers left an explosives-laden car on the road near the office in east Kirkuk's Al-Askari neighbourhood and fled," said Captain Sharzad Mahmud of Kirkuk police.

"The PUK security guards went to check the parked car when it suddenly exploded, killing the two guards and wounding four more, including two guards."

Insurgents have set off a series of car bombs in the past several months against Kurdish party offices in and around Kirkuk, the ethnically volatile oil city claimed both by the Arabs and the Kurds.

Longstanding Kurdish demands for the city to be incorporated in their autonomous region in northern Iraq are to be put to a referendum by December 30.