Iran has blamed Israel for what it called an act of "terrorism" on its Natanz nuclear facility, according to state TV.
Iranian Foreign Minister Mohammad Javad Zarif vowed revenge on Monday, a day after local media reported the incident at the Natanz site, allegedly caused by a problem with the electrical distribution grid.
A foreign ministry spokesman added that Iran would replace any damaged equipment, but that "no contamination or casualties" had been reported.
The Natanz facility is the centerpiece of Iran's uranium enrichment program, one of several monitored by UN nuclear watchdog inspectors.
Israel has in the past accused Iran of trying to build nuclear weapons to use against it.
It has not formally commented on the incident.
However multiple Israeli media outlets have quoted unnamed sources claiming that its Mossad spy service carried out a successful sabotage operation at Natanz, potentially setting back enrichment work there by months.
Iran and several world powers held what they described as "constructive" talks in Vienna last week aimed at reviving the 2015 nuclear deal which U.S. President Donald Trump abandoned three years ago, slapping sanctions on Tehran instead.
Iran has gradually breached many restrictions imposed by the accord, in response to those U.S. sanctions.
The Natanz incident came shortly after Iran, which says its nuclear program is purely for peaceful purposes, began using new and advanced enrichment centrifuges at the facility.
A senior U.S. administration official said Washington had no involvement.