Iran obtained weapons-grade uranium and a design for a nuclear bomb from a Pakistani scientist who has admitted to selling nuclear secrets abroad, according to an exiled Iranian opposition group.
The group, which has given accurate information before, also said Iran is secretly enriching uranium at a military site previously unknown to the United Nations, despite promising France, Britain and Germany that it would halt all such work.
"(Abdul Qadeer) Khan gave Iran a quantity of HEU (highly enriched uranium) in 2001, so they already have some," Mr Farid Soleiman, a senior spokesman for the National Council of Resistance of Iran (NCRI), told reporters.
"I would doubt it was given enough for a weapon," he added.
Mr Soleiman said Khan, who ran a global nuclear black market that supplied Libya and Iran with uranium-enrichment technology until it was shut down earlier this year, also gave Iran a Chinese-developed warhead design sometime between 1994 and 1996.
The International Atomic Energy Agency (IAEA) has said Khan's network gave Libya the bomb design and is trying to find out whether Iran got it too. But it has no proof it did.
Pakistan's mission to the UN in Vienna said it had no knowledge of this allegation and no information to provide. IAEA officials, as well as Iran's UN ambassador, were not immediately available for comment.
The NCRI, like Washington, accuses the Iranian government of secretly developing atomic weapons. Tehran dismisses this allegation, insisting its nuclear programme is peaceful.
The NCRI is the political wing of the exiled group known as the People's Mujahideen Organisation. Both are listed by the US State Department as terrorist organisations.
Iran told France, Britain and Germany on Sunday it would freeze all activities related to enrichment while the two sides negotiate a permanent deal on Iran's nuclear programme. This will protect Iran from being referred to the UN Security Council when the IAEA board of governors meets on November 25th.
The IAEA said in a new report on its two-year investigation of Iran's nuclear programme that Iran had not diverted any of its declared nuclear materials to a weapons programme, but did not rule out the possibility secret atomic activities existed.
The NCRI established its reputation as a nuclear whistleblower in August 2002 when it said the Islamic republic had not declared a massive uranium enrichment plant at Natanz and a heavy water facility at Arak. The allegation was later confirmed and Iran declared the facilities to the IAEA.