A Kirkuk police captain, asking not to be named, told AFP the unidentified assailants had kidnapped the seven family members, among them three of the officer's children.
The officer himself managed to escape during clashes between police and the gunmen, but the seven relatives including a son aged 15 were killed, he said.
Another security official, blaming the Islamic State jihadist group for the attack, said the assailants also blew up a car at the officer's house.