The discovery of the photographs by the Naval Criminal Investigative Service (NCIS) has confirmed a report in the Independent on Sunday two months ago alleging that Marines shot more than 20 Iraqis in a rampage in the town of Haditha last November after one of their number was killed by a roadside bomb.

Initial claims that the civilians died in the explosion, or in crossfire, or that the young men who were killed were armed insurgents, have been demolished by investigators.

One of the most damning items of evidence, it is understood, is a series of mobile phone photographs which show many victims shot at close range in the head and chest, execution-style.

One image shows a mother and young child bent over on the floor as if in prayer. Both had been shot dead.

Whether the photos were intended as 'trophy' items, or whether the Marine who took them was recording evidence against his fellow soldiers, they have supplied crucial corroboration of eyewitness accounts by local people. An Iraqi human rights group also obtained a video, filmed by a local journalism student, which first cast doubt on the official version of events.

Aware that the US military is faced with a scandal which rivals Abu Ghraib, the Pentagon has been briefing members. Official investigations of a rampage by Marines in Haditha are not yet complete, but the Pentagon has briefed Congressmen who will say there are strong indications that civilians were killed without justification.

An official inquiry will not report its final findings until June.