The Atomic Energy Organization of Iran (AEOI) has condemned the attacks of the United States on Iran's nuclear sites in Fordow, Natanz and Isfahan, which it said, contradicts international law, especially the Nuclear Non-Proliferation Treaty (NPT), according to its statement.

"This action, contrary to international law, was unfortunately carried out in the shadow of indifference and even with the cooperation of the International Atomic Energy Agency," the statement said.

The US, through its president, has taken responsibility for the attack on the aforementioned sites, which are under the continuous supervision of the International Atomic Energy Agency, based on the Safeguards Agreement and the NPT Treaty, the AEOI added, according to Mehr News Agency.

IAEA Director-General Rafael Grossi warned of the risk of nuclear contamination from Israel's attacks on nuclear facilities in Iran on Friday in his briefing at an emergency meeting of the UN Security Council.

Talking of serious damage at the Natanz site in Israeli air strikes, Grossi was quoted as saying by Xinhua News Agency as saying: "The main concern inside the facility is chemical toxicity."

Grossi also warned of the serious consequences of an attack on the Bushehr Nuclear Power Plant, which is an operating nuclear power plant and hosts thousands of kilograms of nuclear material, and the Tehran Nuclear Research Reactor.

In a post on X, United Nations Secretary General Antonio Guterres said he is "gravely alarmed by the use of force by the United States against Iran today".

"This is a dangerous escalation in a region already on the edge — and a direct threat to international peace and security," said Guterres.

He also called on all UN Member States to de-escalate and to uphold their obligations under the UN Charter and other rules of international law.

"At this perilous hour, it is critical to avoid a spiral of chaos," said the UN secretary-general.

Analysts have been concerned that potential contamination from the attacked atomic energy sites might be disastrous for the whole region.

Jan Yumul contributed to this report.