Authorities in Iraq say shootings have killed four security members, including two anti-al-Qaida militiamen, in north-central Iraq.

Police officials say the first attack took place early Saturday when gunmen in a speeding car killed two fighters and wounded four at a security checkpoint manned by Sunni Sahwa militiamen in the city of Samarra.

Also, police say they found the bodies of two police officers killed by gunshots to the head in a town near the northern city of Mosul, a day after they were kidnapped.

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.