Half a dozen explosions and fires over the past six weeks at Iranian nuclear, armaments, and electricity facilities and a hospital in north Tehran have rattled the government and shaken Iranians.
There were no immediate reports of any casualties or damage. The US Geological Survey said the 5.1 magnitude quake struck 44 kilometres from the southwestern city of Borazjan and at a depth of 38 kilometres.
US researchers announced a historic nuclear fusion breakthrough on Tuesday, hailing a "landmark achievement" in the quest for a source of unlimited, clean power and an end to reliance on fossil fuels.
The Kalinin nuclear power plant's first, second and fourth reactors were taken offline, Rosenergoatom said in a statement.
US President Donald Trump warned on Monday that Iran is “playing with fire” after Tehran said it exceeded a limit on enriched uranium reserves under a 2015 nuclear deal abandoned by Washington.
Iran on Saturday said it now uses arrays of advanced centrifuges prohibited by its 2015 nuclear deal and can enrich uranium “much more beyond” current levels to weapons-grade material, taking a third step away from the accord while warning Europe has little time to offer it new terms.
The International Atomic Energy Agency told the media on Saturday it was aware of the reports "related to Iran's centrifuge research and development."
What will be the world's northernmost nuclear power plant left Murmansk in Russia's far north on August 23 after being loaded with combustible nuclear fuel.
Iran has committed a further breach of its nuclear deal with major powers by enriching uranium with advanced centrifuges, and plans to install more of those advanced machines than previously announced, a UN nuclear watchdog report showed on Thursday.