The attack, which also wounded at least 70 people, took place during morning rush hour in the center of Kirkuk, news agency reports said. Police fear the death toll may rise as there are still bodies trapped under the collapsed debris of the buildings.
The attackers had apparently sought to take control of the compound, but were foiled, Brig. Gen. Natah Mohammed Sabr, the head of the city's emergency services department, told Agence France-Presse.
"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," an unnamed police official told Reuters.
No group has so far claimed responsibility for the attack.
Sunday’s blast was the third major attack in several weeks in the region, which has an ethnically diverse population of Arabs, Kurds and Turkmen. Kirkuk is at the center of a dispute between the Iraqi government and Kurds over oil and land rights.
A suicide bomber killed 23 people at a Shia mosque in the Iraqi village of Tuz Khurmato on Jan. 23 and days earlier a suicide bomber driving a truck killed 25 in an attack on a political party headquarters in Kirkuk.
Al Qaeda's local wing, the Islamic State of Iraq, and other Sunni Islamist groups are resurgent in Iraq, a fact demonstrated by a persistent wave of attacks since the last American troops left in December 2011.