In a letter to the Security Council, the International Atomic Energy Agency (IAEA) said it was concerned about the "widespread and apparently systematic" dismantling of entire buildings that contained specialised equipment.

Satellite images show the buildings, which housed so-called "dual-use" equipment such as electron beam welders and high-precision milling machines, have disappeared, IAEA Director General Mohamed ElBaradei said in the letter.

Meanwhile, material such as high-strength aluminium has also vanished from open storage areas, he said.

None of dual-use materials found

While the watchdog agency has previously indicated that some military equipment in Iraq later turned up in scrap yards abroad, "none of the high-quality dual-use equipment or materials have been found", ElBaradei said.

"The disappearance of such equipment and materials may be of proliferation significance," ElBaradei said.

The United States blocked the return of IAEA inspectors to Iraq after last year's invasion ousted Saddam from power.

The inspectors left the country just before the war began in March 2003.

US President George W. Bush said Saddam's push for weapons of mass destruction was one reason for launching the war.

But a new report last week from chief US weapons inspector Charles Duelfer concluded that Saddam had stopped trying to build WMD after international inspections were begun following the 1991 Gulf war.

AFP