The Israeli military said on Thursday it had targeted the Arak nuclear reactor in Iran overnight and struck what it said was a nuclear weapons development site in the area of Natanz.
Among its nuclear sites, Iran had a partially built heavy-water research reactor originally called Arak and now Khondab.
Iranian media reported on Thursday morning that air defenses were activated in the area of the Khondab nuclear facility, with two projectiles hitting an area close to it.
Officials told Iranian state TV that evacuations were made prior to the strikes and that no risks of radiation or casualties were detected. There was no mention of any damage.
Natanz, which Israel had previously struck during its six-day-old aerial war with Iran, was the site of a complex at the heart of Iran's nuclear program that included two enrichment plants.
The Israeli military added that it targeted the structure of the reactor's core seal in Arak, which it identified as a key component in plutonium production.
Khondab hosts a partially-built heavy-water research reactor.
Construction was halted under a 2015 nuclear deal between Iran and world powers, and the reactor's core was removed and filled with concrete to make it unusable.
However, Iran informed the UN's nuclear watchdog it planned to start operating the reactor in 2026.
Heavy-water reactors pose a nuclear proliferation risk because they can easily produce plutonium which, like enriched uranium, can be used to make the core of a bomb.
Iran says its nuclear program, the target of Israeli strikes, is purely for peaceful purposes.
The International Atomic Energy Agency, the United Nations’ nuclear watchdog, has been urging Israel not to strike Iranian nuclear sites. IAEA inspectors reportedly last visited Arak on May 14.
Due to restrictions Iran imposed on inspectors, the IAEA has said it lost “continuity of knowledge” about Iran’s heavy water production -- meaning it could not absolutely verify Tehran’s production and stockpile.
As part of negotiations around the 2015 deal, Iran agreed to sell off its heavy water to the West to remain in compliance with the accord’s terms. Even the US purchased some 32 tons of heavy water for over $8 million in one deal. That was one issue that drew criticism from opponents to the deal.