The episode came a day after the country said it had started up advanced uranium enrichment centrifuges at the site, in a breach of its commitments under a 2015 nuclear deal.
Iran has described a blackout at its underground Natanz atomic facility an act of “nuclear terrorism,” raising regional tensions.
Ali Akbar Salehi, the head of the Atomic Energy Organization of Iran, stopped short of directly blaming anyone for the incident. Details remained few about what happened early Sunday morning at the facility, which initially was described as a blackout caused by the electrical grid feeding the site.
An accident at Iran's Natanz nuclear facility on Sunday was the result of a "terrorist" act, the country's nuclear chief Salehi said, according to state TV.
He said the international community and the International Atomic Energy Agency (IAEA) needed to deal with what he called nuclear terrorism. He added that Iran reserves the right to take action against the perpetrators, TV reported.
Reports of Israeli involvement
Many Israeli media outlets offered the same assessment that a cyberattack darkened Natanz and damaged a facility that is home to sensitive centrifuges.
While the reports offered no sourcing for the evaluation, Israeli media maintains a close relationship with the country’s military and intelligence agencies.
Israeli public radio quoted unidentified intelligence sources as saying that Israel's Mossad spy agency carried out a cyber attack against Iran's Natanz nuclear facility. The report on Kan Radio did not disclose the nationality of the intelligence sources.
If Israel caused the blackout, it further heightens tensions between the two nations, already engaged in a shadow conflict across the wider Middle East.
It also complicates efforts by the US, Israel’s main security partner, to re-enter the atomic accord aimed at limiting Tehran’s program so it can’t pursue a nuclear weapon. As news of the blackout emerged, US Defense Secretary Lloyd Austin landed on Sunday in Israel for talks with Prime Minister Benjamin Netanyahu and Israeli Defense Minister Benny Gantz.
Iran reports no injuries or contamination
The incident took place a day after Tehran launched new advanced uranium enrichment centrifuges at the site. The facility, located in the desert in the central province of Isfahan, is the centrepiece of Iran's uranium enrichment programme and is monitored by inspectors of the International Atomic Energy Agency, the UN nuclear watchdog.
Earlier on Sunday, the spokesman for the country's Atomic Energy Organisation (AEOI) had said that a problem with the electrical distribution grid of the Natanz site had caused an incident, Iranian media reported.
The spokesman, Behrouz Kamalvandi, said earlier that "the incident caused no casualties or contamination".
Asked about the incident, an IAEA spokesman said by email, "We are aware of the media reports. We have no comment at this stage."
The spokesman for the nuclear organization announced that an incident took place on Sunday morning in a part of the electricity distribution network of the #Natanz Enrichment Facility.https://t.co/RVjyXPLb1w— Mehr News Agency (@MehrnewsCom) April 11, 2021
"The action taken against the Natanz site shows the failure of the opposition to Iran's industrial and political progress to prevent the significant development of Iran's nuclear industry," Salehi said.
"To thwart the goals of those who commanded this terrorist act ... Iran will continue to improve its nuclear technology on the one hand and to lift oppressive US sanctions on the other hand," he said.
July's mysterious explosion
Natanz suffered a mysterious explosion in July that authorities later described as sabotage.
Israel, Iran's regional archenemy, has been suspected of carrying out an attack there, as well as launching other assaults, as world powers now negotiate with Tehran in Vienna over its nuclear deal.
Iran also blamed Israel for the killing of a scientist who began the country’s military nuclear program decades earlier. Israel has not claimed any of the attacks, though Prime Minister Netanyahu repeatedly has described Iran as the major threat faced by his country in recent weeks.
On Saturday, Iran announced it had launched a chain of 164 IR-6 centrifuges at the plant, injecting them with the uranium gas and beginning their rapid spinning. Officials also began testing the IR-9 centrifuge, which they say will enrich uranium 50 times faster than Iran's first-generation centrifuges, the IR-1.
The nuclear deal limited Iran to using only IR-1s for enrichment.
Since then-President Donald Trump's withdrawal from the Iran nuclear deal in 2018, Tehran has abandoned all the limits of its uranium stockpile. It now enriches up to 20 percent purity, a technical step away from weapons-grade levels of 90 percent. Iran maintains its atomic program is for peaceful purposes, but fears about Tehran having the ability to make a bomb saw world powers reach the deal with the Islamic Republic in 2015.
The deal lifted economic sanctions on Iran in exchange for it limiting its program and allowing inspectors from the International Atomic Energy Agency to keep a close watch on its work.
On Tuesday, an Iranian cargo ship said to serve as a floating base for Iran’s paramilitary Revolutionary Guard forces off the coast of Yemen was struck by an explosion, likely from a limpet mine. Iran has blamed Israel for the blast. That attack escalated a long-running shadow war in Mideast waterways targeting shipping in the region.