The United Nations atomic watchdog challenged Iran on Thursday to disprove American charges it plans to make nuclear weapons and Washington fired a fresh warning at a Tehran government facing pro-democracy protests at home.

Three Iranian opposition supporters set themselves on fire in Rome and Berne, and in Tehran a hardline militia group vowed to defend Iran's Islamic establishment as authorities tried to snuff out pro-democracy protests that have lasted nine nights.

The International Atomic Energy Agency (IAEA) in Vienna criticised Iran's failure to comply with accords designed to stop the use of civilian nuclear resources to make atomic arms.

The IAEA's board of governors urged Iran to be "transparent" and accept without delay or conditions more intrusive, short-notice inspections to dispel U.S. suspicions it was using its nuclear power programme as a cover to develop weapons.

"The board shared the concern expressed by (IAEA chief) Mohamed ElBaradei in his report at the number of Iran's past failures to report material, facilities and activities as required by its safeguards obligations," the IAEA said.

Diplomats said Washington wanted a resolution -- the board's strongest type of statement -- condemning Iran's failures to comply, but shelved the idea due to insufficient support.

While the IAEA statement fell short of a damning resolution, Washington quickly backed it.

"Iran needs to comply. Otherwise the world will conclude that Iran may be producing nuclear weapons," White House spokesman Ari Fleischer told reporters.

"It is international reinforcement of the president's message yesterday that the world, broadly speaking, joins together in fighting proliferation and making certain that Iran does not develop nuclear weapons," Fleischer said, referring to comments made by George W. Bush on Wednesday.

Iran's envoy to the IAEA, Ali Salehi, told reporters later: "We are happy that the board did not go with the pressure to come up with a resolution."

Swiss and Italian authorities quickly doused the flames when two Iranian men in Rome and another in Berne set themselves on fire in a form of protest that Iranian opposition backers have used in Europe since Tuesday to draw attention to their case.

French police briefly detained 180 followers of the Iranian opposition group, the People's Mujahideen, under the Eiffel Tower to prevent more self-immolations and banned further protests.

Authorities said a woman who set herself alight in a Paris protest on Wednesday had died of her burns.

The protesters are angry at the arrest of their leader Maryam Rajavi, head of the group's National Council of Resistance of Iran (NCRI) political arm, and others in Paris on Tuesday.

The French government suspects the group of reinforcing its base in Paris suburbs with a view to launching attacks on Iranian embassies in Europe. The NCRI denies such a plan.

In Tehran, Iran's official IRNA news agency quoted the Basij militia as saying nightly protests against clerical rule had been provoked by the "Great Satan" Washington which was using its "mercenaries" to challenge Iran's Islamic leaders.

"We pledge to defend the sacred Islamic establishment and its achievements as we would our own lives," the militia said in a statement.

The Basij, fiercely loyal to Supreme Leader Ayatollah Ali Khamenei and trained and equipped by the Revolutionary Guards, were out in force in several areas of Tehran on Wednesday night as the protests appeared to be running out of steam.

In a working class suburb of Tehran, riot police stood at key intersections and hardline militants scrutinised the occupants of hundreds of cars carrying would-be protesters.

The heavy security presence, which follows rampaging attacks on demonstrators by vigilantes wielding batons, knives and chains on Friday night, appeared to be working.

The occasional rhythmic blaring of car horns was the only sign of protest and even that was rare.