A video has been posted on an Iraqi extremist website showing the mutilated bodies of Kristian Menchaca and Thomas Tucker, two US soldiers who were captured and killed last month.

The five minutes of footage shows a militant holding up the decapitated head of one of the two soldiers, while another armed militant stamps on the head of the other body, according to the SITE institute which monitors extremist websites.

The bodies of the two soldiers were later found in a ditch, booby-trapped with explosives. Their injuries were so severe that the men had to be identified by their DNA.

The trophy video was posted online days after it emerged that Menchaca and Tucker had been in the same platoon as Steven Green, a former US soldier who has been charged with the rape and murder of a young Iraqi woman and the murder of her family on March 12, while he was serving in Iraq.

Five other US soldiers have also been charged over the alleged rape and killing of Abeer Qassim Hamza, and the deaths of her mother, father and five-year-old sister. It is understood that details of the atrocity against the Iraqi family first emerged in late June, when witnesses came forward.

In their video, however, the al-Qaeda linked Mujahedeen Shura Council sought to claim that the murders of Menchaca and Tucker on June 16 were revenge for the killing of the Iraqi family.

The insurgents claim that as soon as fighters heard of the rape and murder, "they kept their anger to themselves and didn’t spread the news".

"They decided to take revenge for their sister’s honour," the statement said. "With Allah’s help, they captured two soldiers of the same brigade as this dirty crusader. Here are the remains ... to rejoice the hearts of the faithful."

In a statement, the US Army condemned the posting of the video and vowed to find the killers of the two soldiers. "It demonstrates the barbaric and brutal nature of the terrorists and their complete disregard for human life," the statement said.

US investigators say there is no evidence linking the deaths of Menchaca and Tucker to the alleged rape and killing.

Sergeant Paul E. Cortez, Specialist James P. Barker, Private Jesse V. Spielman and Private Bryan L. Howard were charged on Sunday with rape, murder and several other charges. They could face the death penalty if convicted. Sergeant Anthony W. Yribe is charged with failing to report the attack, but is not alleged to have taken part.

The five will face an Article 32 hearing, the military equivalent of a grand jury proceeding, to decide if they should stand trial.

They are charged with conspiring with Mr Green, who was honorably discharged from the Army after he was found to have a personality disorder, and was arrested last month in North Carolina. Mr Green has pleaded not guilty to one count of rape and four counts of murder and is being held in custody.

According to an FBI affidavit, Mr Green and at least two others targeted the young woman and her family for a week before the attack - details of which did not emerge until witnesses came forward in late June.

The soldiers drank alcohol, abandoned their checkpoint, changed clothes to avoid detection and headed to the victims’ house, in the town of Mahmudiyah in the "Triangle of Death", a Sunni Arab area south of Baghdad known for its violence, the affidavit said.

The affidavit estimated that the rape victim was about 25. But a doctor at the local hospital gave her age as 14. He refused to be identified for fear of reprisals.

Mr Green is accused of raping the woman and killing her and the three other family members, including a girl estimated to be 5 years old. An official familiar with the investigation told the Associated Press that Mr Green set fire to the rape victim’s body in an apparent cover-up attempt.

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