UN Secretary-General Antonio Guterres also condemned the US-Israeli strikes and retaliatory attacks by Iran.

"We are witnessing a grave threat to international peace and security," he said, calling for the peaceful settlement of disputes and stressing that lasting peace can only be achieved through peaceful means, including genuine dialogue and negotiations.

The US and Israeli attacks occurred two days after the third round of indirect Iran–US nuclear talks mediated by Oman in Geneva, Switzerland. Technical discussions were scheduled to be held next week in Vienna. Guterres said he was "deeply regretful that this opportunity for diplomacy has been squandered."

"I strongly urge all parties to return immediately to the negotiating table, notably on the Iran nuclear programme," he said.

Amir Saeid Iravani, Iranian ambassador to the UN, described the US-Israel strikes as "war crimes". "This is not only an act of aggression; it is a war crime and a crime against humanity," he said.

"The invocation of 'preemptive attack', claims of an imminent threat, or other unsubstantiated political claims are unfounded legally, morally and politically," Iravani added.

Maged Abdelaziz, the permanent observer of the League of Arab States to the UN, said Saturday's meeting came at a moment that "represents a glaring failure of the multilateral international system, a failure the League of Arab States has long warned against."

He said the Arab-Israeli conflict had expanded into a full-scale regional war and condemned military strikes carried out by Israel and Iran in several Arab countries.

Abdelaziz urged all states to "respect their obligations under international law, including the UN Charter, which clearly prohibits the threat or use of force against the territorial integrity or political independence of any state."

"Any use of force inconsistent with the purposes and principles of the United Nations, especially when it involves attacks on nuclear facilities, could have catastrophic consequences for entire populations," Abdelaziz said. He also called for an immediate halt to hostilities and efforts to prevent further escalation and a wider regional conflict.