They also said a small number of "valuable" missing museum pieces were returned after appeals by Muslim religious leaders, but denied reports from a UN conference that Iraqi officials may have been involved in an organized theft.

"With what I'm expecting has happened in the (archeological) sites in the field and what happened to the Iraq museum, I would say it's the crime of the century because it is really affecting the heritage of mankind," said the head of the National Archaeological Museum in Baghdad, Donny George.

"It looks like there was an action and there were other priorities (for the United States) besides the Baghdad Museum," George told reporters at a briefing about the firestorm over last Friday's ransacking of the museum.

US troops who seized the Iraqi capital on April 9 watched as looters carted away artifacts from some of the world's oldest civilizations.

Under pressure after the museum looting, the United States is sending FBI agents to the Iraqi capital to help with the recovery effort.

But the head of President US George W. Bush's cultural advisory committee has already stepped down in protest at the American failure to prevent the "tragedy."

Jaber Khalil Ibrahim, head of Iraq's General Directorate of Antiquities, said the US and British governments should make amends by preventing any of the antiquities from leaving the country and "look for the objects that will pop up in Switzerland, England, America, Israel and Japan and send them back."

Ibrahim agreed with an assessment by a UNESCO conference of experts called Thursday in Paris to examine the war damage to Iraq's heritage that organised gangs which traffic in works of ancient art were involved in the thefts.

He noted that some of the pieces, such as a 5,000-year-old Sumerian alabaster vase -- known as the Warka vase, which weighs 300 kilogramspounds) -- would need several people to be have been removed.

In the gallery, the only items left were ones too heavy to carry, he added.

"I suspect they really did (know what they were looking for) and that they were especially looking for Sumerian valuable material," Ibrahim said.

But he denied eyewitness reports from the UNESCO meeting which described some of the looters as directed by well-dressed men who had keys to the vaults where they believed the most highly valued items were kept.

He added that "about 20 valuable glazed pottery and some metal" objects were returned in the morning to neighborhood mosques following appeals by imams.

"They said it was their culture which made them bring these things back," he said.

The Iraqi officials confirmed among the other major thefts were the Sumerian vase of Uruk and Akkadian bronze statue of Basitki. A famed 4,000-year-old Sumerian Ur harp was stripped of its gold and badly damaged.

A collection of some 80,000 cuneiform tablets with examples of the some of the world's earliest writing was also taken, and a number of Roman statues were smashed and their heads are missing.

The officials said a final assessment of the losses would take "days and days" since the area, like many parts of the city, is still without power.

Traffickers in Iraqi archaeological items have thrived since the 1991 Gulf War thanks to growing international demand and an economic crisis in Iraq that encouraged people to find innovative ways to make money, experts say.

SPACE.WIRE