By Gideon Long
LONDON - An Iranian exile group said on Wednesday Iran had taken steps to "sanitize" a military plant where it said Tehran had been making bomb-grade uranium for use in nuclear weapons.
Iran denies it is trying to make an atomic bomb, saying its nuclear ambitions are purely peaceful to generate electricity.
The National Council of Resistance of Iran (NCRI), which has given accurate information on Tehran's nuclear sites in the past, said the government began to remove sensitive material from the Lavizan plant after the NCRI publicized details of activity there last Wednesday.
The NCRI said Revolutionary Guards surrounded the plant within hours, closed it to traffic and stopped all staff from leaving.
"(Iranian officials) began to sanitize the site and remove sensitive documents, equipment and materials," a spokesman for the NCRI told a news conference in London.
"During the night, truck movements in and out of the site were reported."
The NCRI, which cited well-placed but disillusioned people within government as its source, accused Tehran last week of using advanced lasers and centrifuges to enrich uranium secretly at Lavizan, in Tehran, and at Parchin, 30 km from the capital.
It said Iran was lying to the United Nations nuclear watchdog about the covert program.
Tehran dismissed those accusations as a "well-timed lie."
Diplomats in Vienna also expressed skepticism about the fact that the NCRI always holds news conferences with what it says are new revelations whenever the U.N. nuclear watchdog meets. The agency's board meets on Thursday to discuss Iran.
On Monday, International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei said his inspectors would only follow up "credible information" and that his experts were trying to determine whether the new NCRI claims were credible.
The NCRI called on IAEA to inspect the facilities before Tehran had a chance to strip them clean.
Iran has been accused by the United States, which branded it part of an "axis of evil" along with North Korea and pre-war Iraq, of using its nuclear power program as a front to build a bomb. Tehran rejects the claim.
Tehran promised the European Union last week it would suspend its entire uranium enrichment program and all related activities in a bid to avoid a report to the U.N. Security Council for possible sanctions.
The suspension took effect on Monday.
Western diplomats say Iran, which has vowed never to dismantle its nuclear program entirely, has asked the EU for permission to continue conducting "research and development" with centrifuges during the freeze.
The EU has refused the request, the diplomats said.