Gunmen killed five Iraqi policemen in a drive-by shooting at a checkpoint in Anbar province, west of Baghdad on Sunday.
"At 8.30am (1330 NZT), gunmen riding in a car and carrying automatic weapons killed five policemen guarding a checkpoint, before fleeing," a police officer in the provincial capital Ramadi said.
He said the gunmen struck in the desert town of Rutbah, on the main highway leading from Baghdad towards Amman and Damascus.
Anbar province was an al-Qaeda stronghold until 2008 when US commanders began recruiting Sunni Arab tribesmen and former insurgents to form militias which turned the tide against the jihadists.
Last month was the deadliest this year in terms of the number of Iraqis killed in attacks, according to government figures. It was the deadliest since June 2008 for US troops, who are due to withdraw by the end of this year.
A total of 271 Iraqis and 14 US soldiers lost their lives.
Iraq has blamed al-Qaeda for the increased death toll, which was up 34 per cent on May. But the US military holds Iranian-backed Shiite militias responsible for the deadly attacks on its troops.