At least four people have been arrested in Iran for trying to sabotage a nuclear site, an Iranian official was quoted by Iranian media as saying on Sunday.
The head of Iran's Atomic Energy Organisation, Ali Akbar Salehi, said officials had monitored and then arrested a "number of saboteurs" before they could carry out their plan.
"Four of these individuals were caught red-handed and their interrogations are ongoing," he said, according to the Mehr news agency on Sunday. He did not identify which nuclear site they were planning to damage or when those detained were arrested.
Israel, widely believed to be the region's only nuclear-armed state, sees Iran's atomic work as a military threat and has said it will attack Iran's nuclear sites if it does not end its programme. Iran says its nuclear work is purely peaceful.
Iran accuses Israel and the West of being behind the assassination of Iranian nuclear scientists and of trying to damage its programme in other ways, such as by cyber attacks.