Iranian officials say they think there was an attempt to sabotage one of Iran's nuclear facilities.
Asghar Zarean, a top security official for Iran's Atomic Energy Organization, accused foreign intelligence agencies of tampering with imported pumps at the Arak heavy-water nuclear reactor.
He said there had been other recent attempts to sabotage Iranian nuclear facilities, but gave no details about who might have been responsible.
The unfinished Arak reactor is seen as capable of producing plutonium, which could be enriched for use in a nuclear weapon.
Iran has previously accused Israel and the United States of using covert operations to cripple its nuclear program.
The allegations come ahead of the scheduled resumption of talks on March 18 between Iran and major world powers on a long-term settlement to the dispute over Iran's nuclear program.
Based on reporting by AP and Reuters