BEIJING - Multiple world leaders expressed concerns after the United States and Israel on Saturday launched "major combat operations" against Iran and Iran retaliated with a series of counterattacks against Israel and US targets across the region.

Casualties were reported and airspace closures spread across parts of the Middle East. The sharp escalation prompted swift international reactions, raising fears of a wider regional conflict and urging an immediate return to diplomacy.

Russian Foreign Ministry denounced the US and Israeli airstrikes as a "premeditated and unprovoked act of armed aggression" against a sovereign United Nations member state in violation of international law, calling for an immediate return to political and diplomatic efforts to resolve regional tensions.

Leaders of the European Union issued a joint statement, expressing concerns over "the developments in Iran" and reaffirming commitments to "safeguarding regional security and stability."

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"We call on all parties to exercise maximum restraint, to protect civilians, and to fully respect international law," said the statement.

France, Germany and Britain jointly clarified that they did not participate in the strikes against Iran and called for a resumption of negotiations.

Several European governments went further, questioning Israel's justification for the operation.

Norway doubted the legitimacy of Israel's so-called "pre-emptive strike," which it emphasized requires "an immediately imminent threat."

Spanish Prime Minister Pedro Sanchez said that Spain rejects the unilateral military action taken by the United States and Israel, warning that it represents an escalation and contributes to a more uncertain and hostile international order.

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Across the Middle East, governments voiced fears that the confrontation could spiral into a broader regional war.

Oman, which has mediated recent US-Iran talks, expressed dismay that negotiations had been undermined and urged an immediate halt to military operations.

Egypt, through a Foreign Ministry statement, warned that the escalating tensions risk spiraling into a wider regional conflict with severe consequences for regional and international security and stability.

The Arab League appealed to all international parties "to work towards de-escalation as soon as possible, to spare the region the scourge of instability and violence, and to return to dialogue."

The Brazilian government urged all parties to respect international law, exercise maximum restraint to avoid escalating hostilities, protect civilians, and safeguard civilian infrastructure.

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Pakistan "regrets the breakdown of talks and outbreak of hostilities in the Middle East," stressing the need for "upholding the international law and principles of the UN Charter" and calling for "all sides to resume diplomacy and find a peaceful and negotiated solution to the crisis."

African Union Commission Chairperson Mahmoud Ali Youssouf on Saturday expressed "deep concern" over military escalation in the Middle East, calling for restraint, urgent de-escalation and sustained dialogue, and warned that further escalation threatens to worsen global instability.

Senegal and Gambia urged an immediate ceasefire and emphasized the need to resolve the crisis through dialogue and diplomacy in accordance with international law.

Mirjana Spoljaric, president of the International Committee of the Red Cross, called on countries to respect the rules of war and urged them to find the political will to prevent "further death and destruction."

UN Secretary-General Antonio Guterres on Saturday condemned the military escalation in the Middle East, saying that the use of force by the United States and Israel against Iran, and the subsequent retaliation by Iran across the region, undermine international peace and security.

"I strongly encourage all parties to return immediately to the negotiating table," he said.