Mr Abbasi-Davani, in unusually strong language for an international forum, also accused the UN nuclear watchdog of a cynical approach and mismanagement and suggested "terrorists and saboteurs" might have infiltrated the organisation.

Iran has often accused Israel and Tehran's Western enemies of being behind the assassination of Iranian nuclear scientists and of trying to sabotage its nuclear programme in other ways.

Mr Abbasi-Davani said explosives had been used to cut power lines from the city of Qom to the Fordow underground uranium enrichment plant on August 17. A day later, he said, IAEA inspectors had asked for an unannounced visit to Fordow.

"Does this visit have any connection to that detonation? Who other than the IAEA inspectors can have access to the complex in such a short time?" Mr Abbasi-Davani asked the gathering in Vienna.

"It should be recalled that power cut-off is one of the ways to break down centrifuge machines," he said, referring to the machines used to enrich uranium, which can have both civilian and military purposes.

His comments came as German Chancellor Angela Merkel said a political solution in the standoff over Iran's nuclear programme is still possible, although she added Tehran posed a threat not just to Israel but to the whole world.

Mrs Merkel said: "I support a political solution and believe we are not at the point where the search for political solutions has been exhausted."

Meanwhile, EU foreign policy chief Catherine Ashton will meet Iran's chief nuclear negotiator Saeed Jalili in Istanbul today.