"We found approximately 200 coffins, each containing bags, each labelled, and each bag contained human remains," said the officer on condition of anonymity.

The remains, which appeared to date back some years, were discovered by the Royal Logistics Corps at a recently-abandoned headquarters of the Iraqi army's 51st division in the town of Al Zubayr.

The division was charged with the defence of the nearby southern city of Basra but abandoned the barracks in the early days of the current US-led campaign to topple Iraqi President Saddam Hussein.

The officer said that the bones appeared to be "quite old".

"They are not from this current conflict, but possibly from the last one," said the officer.

An attempt by the mainly Shiite Muslim people of southern Iraq to rise up against the Sunni dominated regime in Baghdad was brutally crushed by Saddam's security forces in the wake of the 1991 Gulf War.

"The entire area has been sealed off and is being treated as a mass grave," the officer added.

A correspondent from the British Press Association, who is embedded with the British army's Royal Logistic Corps, told of cardboard coffins "stacked five deep in a warehouse" at the site.

A neighbouring building "contained apparent cells and catalogues of photographs of the dead, most of whom had died from gunshot wounds to the head."

"Others were mutilated beyond recognition, their faces burned and swollen in the faded black and white photographs," she reported. "Outside stood what one soldier described as 'a purpose-built shooting gallery'."

She said a tiled plinth, about a foot (30 centimeters) in height, stood in a courtyard, with the brickwork behind it riddled with bullets. Behind it was a drainage ditch.

"Inside the warehouse, one of the bags and coffins contained an identity card written in Arabic, while military webbing and boot soles were visible in others," she reported.

"Human skulls, their teeth broken and missing, looked out from other bags, bundled into the coffins."

SPACE.WIRE