At least one suicide bomber driving a car and gunmen disguised in police uniforms attacked a police headquarters in the northern Iraqi city of Kirkuk, police sources told Reuters.
Initial reports of casualties were unclear. One police official said as many as 30 people could have been killed, but hospital officials in the city said they had received so far only one dead and 50 wounded.
Kirkuk, an ethnically mixed city of Arabs, Kurds and Turkman, is at the heart of a dispute over oil and land rights between Baghdad's central government and the autonomous Kurdistan enclave in the north.
More top news
MI5 face mounting pressure over claims the IS executioner 'Jihadi John', named yesterday as a London graduate, was known to them
Labour leader Ed Miliband is due to set out his party's plans on how it would cut tuition fees.
New drug driving laws are to come into effect next week, including laws on some prescribed medications.