The Iraqi ministry of science and technology informed the IAEA of the disappearance of nearly 380 tonnes of mainly HMX and RDX explosive materiel on October 10, agency spokeswoman Melissa Fleming told AFP, confirming a report in The New York Times.

"It can be used in a nuclear explosion device, for the explosion," she said, adding: "That's why it was under IAEA verification and monitoring" before the March 2003 US-led invasion of Iraq.

The New York Times said the materiel "could produce bombs strong enough to shatter airplanes or tear apart buildings."

Fleming noted: "From a proliferation standpoint there is a possible application in nuclear weapons, (but) the most immediate concern is the threat of the explosive falling in the wrong hands and being used to commit terrorist acts," she said.

The New York Times reported that the explosives disappeared from the sprawling Al-Qaqaa facility, which "was supposed to be under American military control but is now a no man's land, still picked over by looters as recently as Sunday."

The report added: "White House and Pentagon officials acknowledge that the explosives vanished sometime after the American-led invasion."

After UN weapons inspectors left Iraq under US pressure last year, "our only ability ... to monitor these sites is through satellite imagery. It was very difficult to detect here (from IAEA headquarters in Vienna), because the things were in bunkers," Fleming said.

In Portsmouth, New Hampshire, Democratic presidential candidate John Kerry's campaign immediately demanded answers over the missing materiel from President George W. Bush.

"Today, the Bush administration must answer for what may be the most grave and catastrophic mistake in a tragic series of blunders in Iraq," Kerry senior adviser Joe Lockhart said in a statement Monday.

"How did they fail to secure nearly 380 tonnes of known, deadly explosives despite clear warnings from the International Atomic Energy Agency to do so?

"Why was this information unearthed by reporters -- and was it covered up by our national security officials?

"These explosives can be used to blow up airplanes, level buildings, attack our troops and detonate nuclear weapons.

"The Bush administration knew where this stockpile was, but took no action to secure the site."

Fleming said that IAEA chief Mohamed ElBaradei would report to the UN Security Council on Monday.