Explosives were used to cut the electricity power lines to Iran's underground enrichment plant last month, nuclear energy chief Fereydoun Abbasi-Davani told the annual member state gathering of the International Atomic Energy Agency today.

Abbasi-Davani, in unusually strong language in an international forum, also accused the U.N. nuclear watchdog of a cynical approach and mismanagement and suggested that "terrorists and saboteurs" might have infiltrated it.

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.

Abbasi-Davani said explosives had been used to cut power lines from the city of Qom to the Fordow underground uranium enrichment plant on Aug. 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?" Abbasi-Davani told 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.