The BBC has uncovered video footage it says suggests US forces may have been responsible for the deliberate killing of 11 innocent Iraqi civilians in March.
The broadcaster said the images appeared to challenge the US military's account of events which took place in the town of Ishaqi.
US authorities in Baghdad said an investigation was under way, the BBC reported.
Iraqi police have already accused American troops of shooting 11 people, including five children, on purpose in a raid on a house in the town 60 miles north of Baghdad on March 15.
The US military reportedly said at the time that four people were killed during a military operation when a building collapsed under heavy fire.
But the BBC said its tape, which comes in the wake of the alleged massacre in Haditha in November, showed a number of dead adults and children at the site with gunshot wounds.
It added however that it did not appear the Iraqis had necessarily been shot at close range, as locals had suggested.
The pictures came from a hardline Sunni group opposed to coalition forces.
The BBC said it had been cross-checked with other images taken at the time of the events and was believed to be genuine.
It said the US had previously said the firefight began after a tip-off that an al Qaida supporter was visiting the house, and that the bodies of a suspect, two women and a child were found in the rubble of the fallen building.
US investigations are under way into accusations that the US marines killed up to 24 Iraqi civilians in Haditha and covered up the deaths.
Yesterday the American military announced that coalition troops in Iraq were to have ethical training for the next 30 days.Reuse content