Iran has begun moving machines that enrich uranium to an underground bunker near the holy city of Qom, a senior official said, a move likely to fan Western fears of an Iranian advance toward nuclear weapons capability.
His announcement was a further sign of the Islamic state's determination to press ahead with enrichment in defiance of international demands that it desist from such activity, which Tehran says will be for peaceful applications only.
"Transferring Natanz centrifuges to Fordow (near Qom) is under way with full observance of standards," Fereydoun Abbasi-Davani told state broadcaster IRIB. "Fordow's facilities are being prepared and some centrifuges have been transferred."
Iran announced in June that it would shift its production of higher-grade uranium from its main enrichment complex in the central city of Natanz to the subterranean site at Fordow.
Iran, the world's No. 5 oil exporter, denies Western accusations it is seeking to develop nuclear bombs, saying its enrichment program is meant solely to provide an alternative source of electricity or isotopes for medicine and agriculture.
Iran only disclosed the existence of Fordow to the U.N. nuclear watchdog in September 2009 after learning that Western intelligence agencies had detected the mountain site.
Moving enrichment activity to the underground bunker could offer greater protection against any attacks by Israel or the United States, which have both said they do not rule out pre-emptive strikes to stop Iran getting nuclear weapons.
In Vienna, a senior Western diplomat criticized Iran's move.
"The announcement calls attention to Iran's continuing refusal to abide by its international obligations, including the U.N. Security Council's prohibition against Iran installing or operating any centrifuges," the diplomat said.
"Iran's provocative behavior reinforces the need to fully implement international sanctions against Iran."
The Islamic Republic also said in June that it aimed to triple its capacity to enrich uranium to a higher grade — 20 percent fissile purity — which it says will be used to replenish the fuel stock for a medical research reactor.
Western officials and analysts say that by producing 20 percent enriched material Iran has taken a significant step closer to the 90 percent threshold suitable for atom bombs.
The United Nations' International Atomic Energy Agency (IAEA) declined Monday to comment on Abbasi's statement.
In an interview with Reuters Friday, IAEA Director General Yukiya Amano said that moving centrifuges to Qom and increasing enrichment capacity was a "further deviation" from several Security Council resolutions, which demand that Iran suspend all enrichment-related activities to foster serious negotiations on a peaceful solution to the dispute.
Amano said the IAEA was in talks with Iran on how its inspectors would effectively monitor activities at Fordow.
"What we are doing is that we are monitoring and we are negotiating the new safeguard approach to verify the activities," he said.
Last week Russia began a fresh diplomatic campaign to re-engage Iran in nuclear talks with world powers that stalled in January over Iran's insistence on its right to enrich uranium despite U.N. resolutions calling on it to stop.