Updated

Iraqi authorities say gunmen have killed four Sunni anti-al-Qaida militiamen in a town north of Baghdad.

A police officer said the Saturday attack took place when gunmen in three speeding pickup trucks fired on a security checkpoint manned by Sahwa fighters in the town of Tarmiyah, 50 kilometers (30 miles) north of Baghdad.

The police officer added that five other Sunni fighters and two civilians were wounded in the attack.

Medical officials confirmed the casualty figures. All officials spoke on condition of anonymity as they weren't authorized to release the information.

Insurgents frequently attack members of the Sahwa, which joined forces with U.S. troops at the height of the Iraq war to fight al-Qaida.