The motion brought by Britain, France and Germany -- but opposed by China and Russia -- is the first of its kind since November 2022 and comes amid an impasse over Iran's escalating nuclear activities.

Western powers fear Tehran may be seeking to develop a nuclear weapon, a claim Iran denies.

The resolution was carried by 20 votes in favour -- including the United States, which initially was reluctant for fear of aggravating Middle East tensions -- with 12 abstentions and one country not participating, diplomats told AFP.

The confidential document obtained by AFP reiterates it is "essential and urgent" that Tehran provide "technically credible explanations" for the presence of uranium particles found at two undeclared locations in Iran.

"A continued failure" by Iran to provide full cooperation on the years-long probe "may necessitate" a comprehensive assessment by IAEA chief Rafael Grossi, the text said.

- 'Devoid of any legal basis' -

The resolution also says Iran has to "reverse its withdrawal of the designations of several experienced Agency inspectors", and "without delay" reconnect the cameras used to monitor nuclear activities.

The text also notes the "concerns" surrounding "recent public statements made in Iran... regarding its technical capabilities to produce nuclear weapons and possible changes to Iran's nuclear doctrine".

Following intense negotiations with the United States, the resolution was modified to secure Washington's support.

Although symbolic in nature at this stage, the censure motion aims to raise diplomatic pressure on Iran, with the option to potentially refer the issue to the UN Security Council.

In the past, similar resolutions have prompted Tehran to retaliate by removing surveillance cameras and other equipment from its nuclear facilities and ratcheting up its uranium enrichment activities.

Tehran, which has already threatened "a serious and effective response, slammed the censure motion as "devoid of any legal, technical and political basis".

- 'Alarming levels' -

While Tehran denies that it is seeking to develop a nuclear weapon, it has at the same time significantly ramped up its nuclear programme and now has enough material to build several atomic bombs.

During the debates at the IAEA Board of Governors that began on Monday in Vienna, European powers denounced Iran's expansion of its nuclear programme "to alarming levels" as "unprecedented for a state without a nuclear weapons programme".

According to the IAEA, Iran is the only non-nuclear weapon state to enrich uranium to the high level of 60 percent -- just short of weapons-grade -- while it keeps accumulating large uranium stockpiles.

"Iran's escalating nuclear activities significantly harm international security and undermine the global non-proliferation architecture," Britain, France and Germany, known as the E3, said in a separate statement.

Iran has gradually broken away from its commitments under the nuclear deal it struck with world powers in 2015.

The landmark deal provided Iran with relief from Western sanctions in exchange for curbs on its atomic programme, but it fell apart after the unilateral withdrawal of the United States under then-president Donald Trump in 2018.

Efforts to revive the deal have so far failed.

In a joint statement quoted Wednesday by Iran's official news agency IRNA, Tehran, Moscow and Beijing called on "Western countries to show political will... and take the necessary steps to resume the implementation" of the 2015 nuclear deal.

But the United States rejected that assertion as "a tired and transparent gambit".

"Iran refused a deal when it was possible, continued with activities that negated the chance for that deal, and now makes baseless statements to obfuscate the history," the US said in its national statement to the board.

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