Brig. Gen. Natah Mohammed Sabr, head of the city's emergency department, said the militants attempts to take control of the compound housing police headquarters failed, al-Arabiya reported. He said at least 70 people were injured in the attack.
Officials said the number of casualties was expected to rise.
Iraqi security forces killed two suicide bombers attempting to enter the Kirkuk Police Command center before they detonated their bomb belts, IraqiNews.com said.
"The police forces shot the two suicide bombers dead after breaking into the building before they managed to detonate their explosive belts," a security source told the Iraqi website.
Sabr said the attack occurred during rush hour in the city center and the militants were armed with guns, grenades and suicide vests when they attempted to force their way into the building. A nearby building was severely damaged, he added.
No one claimed responsibility for the attack, however, al-Arabiya noted the city is located in a disputed area claimed by both the central government and Iraq's autonomous Kurdish region.With its massive oil reserves, Kirkuk is the most bitterly contested of Iraq's disputed territories, the BBC said.