21 Iraqi guardsmen were kille

"The attackers disarmed the police, gathered them together and then shot them dead," according to a local police officer.

Iraqi police Caption Mohammed Kamal said that the US occupation forces had imposed a curfew on the restive city, ordering its residents to stay at homes or risk being shot.

The new attack come only 24 hours after 33 Iraqis were killed and 48 others injured in four car bombings and attacks in Samarra, north of Baghdad.

Two weeks ago, 49 Iraqi army recruits were similarly massacred as they headed home in minibuses from western Iraq after completing a training course.