Two American soldiers were killed in restive Anbar province west of the capital, the US command said. It said only that they died "due to enemy action".

The suicide driver struck during a football match between local teams in Hadhra, 180 miles north of Baghdad. Seven of the dead were spectators and the other three were policemen providing security for the game.

The attack occurred the day after a pair of bombs exploded on a football field in Baghdad, killing 11 young players and spectators. No group claimed responsibility for either attack.

In Mosul, armed clashes erupted on Friday after a car bomb killed four police officers, including a colonel.

Eight insurgents were killed and five cars rigged with explosives were found before order was restored, police Maj Gen Withiq al-Hamdani said.

Also on Friday, two people were killed and four wounded when three mortar shells exploded in a religiously mixed suburb near Baghdad. Earlier in the day, an engineer was fatally shot in the capital and an unidentified body was found elsewhere in the city, police said.

Three were killed when a group of Shi'ites returning home in a bus from a pro-Hezbollah demonstration in Baghdad came under fire from unidentified gunmen on Friday.

Five other buses carrying Shi'ite demonstrators also came under attack by gunmen elsewhere, injuring 20 people.

In Baghdad, unidentified gunmen rushed into a mobile phone shop, killing the owner, Ahmed Hassan, and injuring his two brothers.

In Kut, 100 miles southeast of Baghdad, six bodies were found in the Tigris, four of them decapitated, officials said. It appeared they were victims of sectarian death squads responsible for escalating Sunni-Shi'ite conflict. Another unidentified body of a man was found in alAzeziya, 50 miles south of Baghdad.

Police said gunmen barged into the home of a Shi'ite family late on Thursday in Dujail, 50 miles north of Baghdad, killing four and wounding eight.

Also on Friday, the US military said American forces killed at least three insurgents during an air strike and multiple raids southeast of Baghdad the day before.