The director-general of the International Atomic Energy Agency, or IAEA, on Friday told the agency's board of governors that "nuclear facilities must never be attacked, regardless of the context or circumstances, as it could harm both people and the environment".

In a statement, Rafael Mariano Grossi said the IAEA is currently in contact with the Iranian nuclear safety authorities to ascertain the status of relevant nuclear facilities after airstrikes by Israel, and to assess any wider impact on nuclear safety and security.

"At present, the competent Iranian authorities have confirmed that the Natanz enrichment site has been impacted and that there are no elevated radiation levels," he said. "They have also reported that at present, the Esfahan and Fordow sites have not been impacted."

Addressing the air strikes, he said, "This development is deeply concerning ... such attacks have serious implications for nuclear safety, security and safeguards, as well as regional and international peace and security."

According to media reports, at least six nuclear scientists are known to be among those killed in the strikes.

Israel said its actions were a preemptive move targeting what it called Iran's program to develop nuclear weapons and to "neutralize an immediate and existential threat to our people". Iran insists its nuclear program is peaceful.

Earlier, Iran rejected what it called the IAEA board's "anti-Iran resolution", which alleged inappropriate Iranian progress in nuclear enrichment.

According to a report by the Islamic Republic News Agency, a joint statement by the Ministry of Foreign Affairs and the Atomic Energy Organization of Iran on Thursday said that in response to the resolution, a new uranium enrichment facility had been ordered in a "secure location" and "first-generation centrifuges at the Fordow enrichment site would be replaced with sixth-generation machines".