Police officials say the attack took place in the morning in Injan village, about 120 kilometres (75 miles) north of Baghdad.
A suicide bomber first rammed his explosive-laden truck into the building. This was followed by a firefight between other attackers and policemen.
The brigade commander, Brig Ragheb al-Omari, and his assistant officer were among the dead.
Medical officials confirmed the casualties. All officials spoke on condition of anonymity as they were not authorised to speak publicly to journalists.