The attack took place soon after midnight about 500 kilometres (310 miles) west of Baghdad in mostly Sunni Anbar province, according to a police officer in Ramadi, the provincial capital.

Five policemen, including a lieutenant, were killed, he said on condition of anonymity.

One of the attackers was killed in clashes that ensued between the gunmen and police, while the others set off a bomb attached to a nearby caravan and, using that as a distraction, fled the scene.

The total number of gunmen who carried out the assault was not clear.

A medic at Ramadi hospital confirmed the facility received the bodies of the five policemen killed, and that they died of gunshot wounds.