Iran's former arch-rival in the region, Saudi Arabia, which has been engaged in a Chinese-brokered detente with Tehran since 2023, expressed "great concern" over the attacks.

Gulf countries have been engaged in a diplomatic frenzy for solutions since Israel launched its air campaign on their neighbour Iran on June 13.

Many of the oil-rich countries host major US assets and bases and fear that a spillover from the war could threaten their security and economy.

Qatar, host of the biggest US military base in the Middle East, said it feared "catastrophic consequences" for the region and the entire world.

Yemen's Huthi rebels repeated threats to target US vessels and warships in the Red Sea after the overnight strikes, describing them as a "war declaration" on the Iranian people.

On Saturday, the Iran-backed group threatened to resume attacks on US vessels and warships in the Red Sea despite a recent Oman-mediated truce, should Washington strike Iran.

US President Donald Trump said the attacks destroyed Iran's main nuclear sites, describing them as a "spectacular military success".

But his allies in the Gulf, who neighbour Iran, were urging a return to diplomacy.

Oman, which was mediating nuclear talks between Washington and Tehran, strongly condemned the US strikes labelling them illegal and calling for immediate deescalation.

The United Arab Emirates expressed concern after the attack, calling for "an immediate end to the escalation".

Bahrain, home to a major US naval base, told most of its government employees to work from home until further notice following the escalation.

The US Navy's Fifth Fleet, which covers the region, is based in Bahrain.

Kuwait said its finance ministry had activated an emergency plan that includes readying shelters.

The Palestinian militant group Hamas condemned what it called "blatant US aggression" against Iran.

Iraq, which also hosts US bases, expressed "deep concern and strong condemnation" of the attacks, government spokesperson Basim Alawadi said, labelling them "a grave threat to peace and security in the Middle East".

Fears are growing in Iraq over a possible intervention by Iran-backed armed factions, who have threatened Washington's interests in the region if it were to join Israel in its war against Iran.

Lebanese President Joseph Aoun, largely seen as close to the United States, urged both sides to resume talks to restore stability in the region.

The country has been reeling from a destructive conflict between Israel and the Iran-backed Hezbollah group over the Gaza war, which ended with a fragile truce last November despite frequent Israeli attacks on the group.

Egypt also condemned the escalation in Iran, warning of "dangerous repercussions" for the region and calling for diplomacy.