Iran on Friday rejected allegations in a new International Atomic Energy Agency report that it was frustrating UN inspection of a suspect military site by apparently scrubbing it clean.
"These statements have no technical basis. Anyone who has expertise in this area knows that these statements are mere pretexts and that one cannot clean a site" of nuclear work, Foreign Minister Ali Akbar Salehi told the ISNA news agency.
The restricted report, seen by AFP on Thursday, says the IAEA's ability to inspect Parchin has been "significantly hampered" by the clean-up.
It repeated its suspicions that the base might have been used for experiments using conventional explosives to design a nuclear warhead, and stressed that Iran has repeatedly refused access to the site on the grounds it was a non-nuclear facility.
The IAEA report also said Iran has doubled its uranium enrichment capacity at an underground nuclear facility in Fordo by installing more than 1,000 new centrifuges, although they have not been put into operation.
The IAEA said it was still "unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities."
Western and other governments suspect Iran has been trying to develop a nuclear weapons break-out capability. Tehran denies any such ambition, insisting its nuclear programme is exclusively for power generation and medical purposes.