Iran blamed Israel for "sabotaging" its underground nuclear plant in the Natanz compplex in a cyber attack that triggered a power outage, damaging centrifuges used to enrich uranium, The Tribune reported.
Iran warned it would retaliate for the attack, as Israel appeared to confirm allegations that it was involved in a cyber-attack on the Iranian nuclear facility on Sunday.
Reports in multiple Israeli media outlets quoted intelligence officials saying Israel's national intelligence agency, Mossad, was responsible for the incident.
The attack was carried out hours after officials at the Natanz nuclear reactor restarted the upgraded centrifuges that could accelerate the production of enriched uranium, in what had been considered as an important milestone in Iran's nuclear program.
Centrifuges are devices needed to produce enriched uranium from spent fuel rods used in power plants, which can then be used to build nuclear bombs.
"Fortunately, the incident did not cause any human injuries or leaks," CNN quoted Behrouz Kamalvand, spokesperson for Iran's Atomic Energy Organization, as saying.
The AEO said an investigation is underway and further information will be announced later.
Ali Akbar Salehi, Iran's nuclear director, urged the international community and the International Atomic Energy Agency to take action against the perpetrators of the attack that was initially described as a blackout caused by the electrical grid feeding its underground enrichment halls.
If Israel was behind the sabotage, it would further escalate tensions between the two countries, already engaged in a shadow conflict across the Middle East for many years, analysts say.
The latest incident comes as diplomatic efforts to restart a stalled 2015 nuclear agreement, which the U.S. withdrew from under the Trump administration in 2018, have resumed.
Israeli Prime Minister Benjamin Netanyahu, who met Sunday with U.S. Defense Secretary Lloyd Austin, said he will do everything in his power to stop the nuclear deal between Tehran and Washington.