Iran's nuclear chief called a blackout at the country's Natanz facility Sunday an act of "nuclear terrorism."
"While condemning this desperate move, the Islamic Republic of Iran emphasizes the need for a confrontation by the international bodies and the (International Atomic Energy Agency) against this nuclear terrorism," Ali Akbar Salehi said, according to state TV.
Salehi stopped short of blaming anyone for the alleged attack.
State TV reported a problem with the electrical distribution grid of Natanz - just hours after starting up a cascade of centrifuges for producing enriched uranium.
The spokesman for the Atomic Energy Organization of Iran (AEOI), Behrouz Kamalvandi, said, "The incident caused no casualties or contamination."
The IAEA, the United Nations body that monitors Tehran's atomic program, said Sunday that it was aware of the situation and following developments, but did not elaborate.
Multiple Israeli media outlets reported Sunday that Israel could have been behind the blackout, which may have been a cyberattack.
The Natanz facility has been subject to attacks in the past, including the Stuxnet cyberattacks nearly a decade ago, which was widely blamed on the United States and Israel. Natanz also suffered a mysterious explosion of its centrifuge assembly plant last July, which Iranian authorities described as sabotage.
The U.S. and Israel have not commented on the latest blackout.
The incident came one day after Iranian President Hassan Rouhani oversaw on live television the launch of advanced centrifuges to enrich uranium, a key component for nuclear weapons, while reiterating his country's commitment to nuclear non-proliferation.
Rouhani reiterated claims that the country's nuclear activities are "peaceful and for non-military purposes," but the latest actions may have been another in a series of breaches of the 2015 nuclear deal Iran reached with world powers.
The United States and Iran held indirect talks in Vienna last week and agreed to a second round this week to try to bring each other back into compliance with the deal, known formally as the Joint Comprehensive Plan of Action. Iran has maintained that all U.S. sanctions against it be lifted and the U.S. warned that such a demand may lead to an impasse. U.S. President Joe Biden has pledged to return to the JCPOA if Iran first resumes full compliance.
Then-U.S. President Donald Trump pulled the U.S. out of the agreement in 2018 and a reimposition of American sanctions on Iran became a major irritant in relations between the U.S. and Europe. The Islamic Republic in turn began taking steps away from its commitments as it sought sanctions relief, including holding larger stockpiles of enriched uranium and enriching the material to higher levels.