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UN spokesman Hiro Ueki said 11 chemical rocket warheads - and a 12th that requires further evaluation - were uncovered at the Ukhaider depot, south of Baghdad.

"The warheads were in excellent condition and were similar to ones imported by Iraq during the late 1980s," Mr Ueki said in Baghdad on Thursday.

None of the weapons had been declared by the Iraqi Government, he added.

More tests needed

Mr Ueki did not elaborate on the significance of the find - but the UN office in Baghdad has since told the BBC that they did not immediately consider the discovery to be a "smoking gun".

Senior European Union officials welcomed the announcement as evidence that UN weapons inspections were effective.

"This is proof of the work of the inspectors," EU foreign policy chief Javier Solana said.

"I think we have to wait to see the results of their analysis."

Mr Solana was speaking in Greece, which currently holds the EU presidency.

BBC defence correspondent Jonathan Marcus says that on its own the discovery may not be a smoking gun, but it may be viewed by the US and Britain as part of a pattern of infringements by Iraq.

KEY DATES

16 Jan - Chief UN inspector Hans Blix briefs EU 19 Jan - Blix meets top Iraqi officials in Baghdad 27 Jan - First full report on inspections presented to UN 29 Jan - UN discusses report 31 Jan - Bush meets Blair 15 Feb - Anti-war protests across Europe 27 Mar - Blix submits new report to UN

Next steps in full

Much, our correspondent says, now depends on how chief weapons inspector Hans Blix assesses the discovery.

The find comes shortly after Mr Blix called on Iraq to do more to substantiate its claims that it has destroyed banned weapons, or risk a US-led war.

Mr Blix, briefing EU officials in Brussels, said Iraq had either to provide evidence - such as archives and budgets - that it had destroyed suspected weapons of mass destruction, or surrender what it might have for destruction.

'Important date'

The chief Iraqi liaison officer, General Hossam Mohammad Amin, called the discovery a "storm in a teacup".

General Amin: much ado about nothing

"These rockets are expired," he said. "They were in closed wooden boxes that we had forgotten about."

The US reacted cautiously to the announcement.

The US ambassador to the United Nations, John Negroponte, called the find an "interesting development" but cautioned against jumping to conclusions.

"I'm sure that we will be getting further information, but I certainly can't enter into that kind hypothetical proposition without having more facts at our fingertips," Mr Negroponte said.

Earlier on Thursday White House spokesman Ari Fleischer insisted that the submission of Mr Blix's progress report to the UN on 27 January is "an important date".

"Beyond that, events will dictate timetables," he said.