Iraqi authorities say insurgents have attacked a security headquarters in a northern city, killing four people.

Police officials say the assault on Wednesday took place when a car bomb exploded at the gate of the Police Intelligence Department in the religiously-mixed city of Kirkuk. Later, suicide bomber entered the building and set off his explosive belt among police members.

A gunbattle between attackers and security forces erupted immediately after the bombings, said police. They said another 46 people were wounded.

Hospital officials, who spoke on condition of anonymity because they were not authorized to speak to media, confirmed the casualty figure.

Wednesday's attack came only one day after a similar assault on a mayor's office in the Sunni town of Tarmiyah that left 10 people dead.