A huge amount of explosives were looted from the Al Qaqaa ammunition site in Iraq while US soldiers assigned to guard the material watched "helplessly," unidentified American soldiers were quoted as saying.

About a dozen US troops were guarding the sprawling facility in the weeks after the April 2003 fall of Baghdad when Iraqi looters raided the site, the Los Angeles Times newspaper quoted the soldiers as saying.

Some soldiers sent messages to commanders in Baghdad requesting help but received no reply, they said.

The witness accounts reported by the Los Angeles Times are the first provided by US soldiers. They bolster claims that the US military had failed to safeguard the explosives, the newspaper noted.

Iraqi officials told the United Nations International Atomic Energy Agency last month that about 380 tonnes of high-grade explosives, powerful enough to detonate a nuclear weapon, had been taken from the Al Qaqaa facility.

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The soldiers, who belong to two different units, described how Iraqis snatched explosives from unsecured bunkers and drove off with them in pickup trucks.

The soldiers said they could not confirm that looters took the particularly powerful explosives known as HMX and RDX. One soldier, however, said US forces saw looters load trucks with bags marked "hexamine," which is a key ingredient for HMX.

Four soldiers, who are members of the Germany-based 7th Support Centre and the 258th Rear Area Operations Centre, an Arizona-based army National Guard unit, said the looting happened over several weeks in late April and early May, 2003.

Asked about the soldiers' account, Pentagon spokeswoman Rose-Ann Lynch said, "We take the report of missing munitions very seriously. We are looking into the facts and circumstances of this incident."