The resolution was the first by the 35-nation board of the International Atomic Energy Agency (IAEA) against Iran in almost four years, and a sign of growing alarm over Tehran's failure to dispel fears it has clandestine plans to build nuclear bombs.
It passed by a 25-3 margin with six abstentions, smoothed by rare backing from Russia and China, which have blocked global attempts to isolate Iran, a trade partner for both, in the past.
Russia called on Iran to "react with full seriousness to the signal contained in the resolution … and to ensure full cooperation with the agency." Moscow and Beijing's support is seen as vital to the success of international pressure on Iran.
The vote reflected exasperation with Iran's retreat from an IAEA-brokered draft deal to provide it with fuel for a medical nuclear reactor if it agreed to part with its enriched uranium, which could be turned into bomb material if further refined.
British Prime Minister Gordon Brown said major powers would have to pursue harsher sanctions against Iran if it ignored the vote. This, he said during a visit to Trinidad, sent "the clearest possible signal to Iran that they should desist from their nuclear plans, that the world knows what they are doing."
U.S. IAEA envoy Glyn Davies called the resolution "a signal that patience is running out."
"We can't have round after round of fruitless negotiations, circular negotiations that don't get us where we want to get," he said, referring to perceptions Iran is stringing out inconclusive talks to buy time to stockpile enriched uranium.
Davies said it was imperative for Iran to "live up to its international obligations and offer transparency in its nuclear programme, rather than carry out more evasions and unilateral re-interpretations of its obligations."
The measure won blanket Western backing. Cuba, Malaysia and Venezuela, prominent in a developing nation bloc that includes Iran, voted "no," while Afghanistan, Brazil, Egypt, Pakistan, South Africa and Turkey abstained. Azerbaijan missed the ballot.
Iran denies seeking nuclear weapons, saying its atomic energy programme is purely for peaceful purposes. But its record of clandestine nuclear work and curbs on IAEA inspections have stoked suspicions and a seven-year standoff with world powers.
Iranian Ambassador Ali Asghar Soltanieh called the resolution, which also urged Iran to immediately freeze the Fordow enrichment project hidden inside a mountain bunker, a "hasty and undue" step devoid of legal basis.
IRAN SAYS WILL IGNORE RESOLUTION
"The great nation of Iran will never bow to pressure and intimidation vis a vis its inalienable right to peaceful uses of nuclear energy," he said.
"We will not implement any word of it because this is a politically motivated gesture against the Iranian nation."
He said Iran would continue to allow basic inspections at its nuclear sites but stop making "voluntary gestures" of extra cooperation such as when it allowed widened surveillance at its rapidly expanding main enrichment complex at Natanz.
Soltanieh said the resolution would also poison the atmosphere for further talks with the United States, France, Britain, Germany, Russia and China launched on October 1 in Geneva, where the reactor fuel plan was agreed in principle.
"Such gestures … are certainly destructive. They spoil the existing cooperative environment. But neither sanctions nor the threat of military attacks can interrupt our peaceful nuclear activities even for a second," he said.
Iran admitted Fordow's existence in September, at least two years into its construction, shocking IAEA inspectors. Western diplomats said Iran was forced to come clean after learning the site had been detected by their spy services.
Fordow's emergence fanned suspicions there are more secret sites intended to produce atom bombs, since experts said the plant's capacity was too small to feed a civilian nuclear power plant, but big enough to make weapons material.
The resolution urged Iran to document the timeline and original purpose of Fordow and confirm it has no more hidden atomic facilities or clandestine plans for any. Soltanieh said those demands were beyond Iran's legal obligations.
Iran has told the IAEA it developed the Fordow site in secret as a backup for other, known facilities in case they were bombed by Israel, which deems the Islamic Republic's expanding nuclear programme "an existential threat."
The last IAEA board resolution slapped on Iran was in February 2006, when governors referred Tehran's dossier to the U.N. Security Council over its refusal to suspend enrichment and open up completely to IAEA inspections and investigations.
Iran had assured the IAEA last year it was not hiding any nuclear-related activities in violation of transparency rules.
Friday's resolution voiced "serious concern" at the Fordow cover-up and said this blatantly defied U.N. Security Council demands dating from 2006 for a suspension of sensitive nuclear activity to foster good-faith negotiations.
(Additional reporting by Sylvia Westall in Vienna and Adrian Croft in Trinidad; editing by Andrew Roche)
