Meanwhile five people were killed and the remains of at least 18 people, including eight heads tucked inside a fruit crate, turned up around the capital as the government prepared to fill a pair of security ministries which many hope will help stem the rampant violence.

The military said that its investigation into a deadly raid on March 15 in the town of Ishaqi, south of Samarra, had shown no evidence of misconduct by US troops.

"The investigation revealed the ground force commander, while capturing and killing terrorists, operated in accordance with the rules of engagement governing our combat forces in Iraq."

The investigating officer "ascertained that the ground force commander properly followed the rules of engagement as he necessarily escalated the use of force until the threat was eliminated."

US officials said that four people died in the raid after US forces were tipped off that a supporter of al-Qaeda was visiting a house in Ishaqi.

The BBC this week showed footage of 11 bodies, including women and children, part of a video which it said it received from a Sunni Arab group opposed to US forces in Iraq, evidence it said appeared to contradict the US version of events.

A report filed by Iraqi police accused US troops of rounding up and deliberately shooting 11 people in the house, including five children and four women, before blowing up the building.

"Allegations that the troops executed a family living in this safe house, and then hid the alleged crimes by directing an air strike, are absolutely false," the US military said.

The probe report came as the Pentagon was investigating an alleged massacre by US marines of 24 unarmed Iraqi civilians in the town of Haditha last year.

A separate inquiry is looking into whether there was a cover up over involvement in the killings.

Time magazine has said marines killed seven people in one house and then another 12 people in neighbouring homes, as well as shooting dead the driver and four passengers of a passing taxi.