A US defence official said no one was hurt in the attack -- which Trump said Iran had given advanced notice of -- and oil prices sank afterwards as traders breathed a sigh of relief at what one analyst called the "somewhat measured" response.

Qatar, which lies 190 kilometres (120 miles) south of Iran and is home to the largest US military facility in the Middle East, said its "air defences successfully intercepted a missile attack targeting Al Udeid Air Base".

Iran's National Security Council confirmed having targeted the base "in response to the US aggressive and insolent action against Iran's nuclear sites and facilities".

In its statement, the council said the number of missiles used "was the same as the number of bombs that the US had used", in a signal that it had calibrated its response to be directly proportional.

After more than a week of Israeli strikes on nuclear and military targets across Iran, the United States joined its ally's campaign on Sunday, carrying out attacks on three key Iranian nuclear facilities, including on an underground uranium enrichment facility at Fordo using massive bunker-busting bombs.

"Iran has officially responded to our Obliteration of their Nuclear Facilities with a very weak response, which we expected, and have very effectively countered," Trump posted on his Truth Social platform after the attack, thanking Tehran "for giving us early notice, which made it possible for no lives to be lost, and nobody to be injured".

Adding that Iran had "gotten it all out of their 'system'," he said: "Perhaps Iran can now proceed to Peace and Harmony in the Region, and I will enthusiastically encourage Israel to do the same."

The New York Times, citing Iranian officials, reported that the response had been designed to allow "all sides an exit ramp", drawing a parallel to a similar Iranian attack on a US base in Iraq following Washington's assassination of top Iranian general in 2020.

With international concern mounting that Israel's campaign in Iran could lead to a regional spillover -- concern that only intensified after the US strikes -- French President Emmanuel Macron said after the Iranian retaliation that "the spiral of chaos must end".

- 'Right to respond' -

Iran's security council maintained that its "action does not pose any threat to our friendly and brotherly country, Qatar".

But Qatari foreign ministry spokesman Majed Al-Ansari said his country "reserves the right to respond directly in a manner proportional to the nature and scale of this blatant aggression".

Its much larger neighbour Saudi Arabia, historically a rival of Iran, condemned Tehran's attack and offered "all its capabilities to support the sisterly State of Qatar in any measures it takes".

AFP reporters heard blasts in central Doha and in Lusail, north of the capital, on Monday evening, and saw projectiles moving across the night sky.

The US defence official said Al Udeid was "attacked by short-range and medium-range ballistic missiles", and Ansari said it had been evacuated as a precaution ahead of time.

Iran's Revolutionary Guard Corps said six missiles had hit the base, according to state media.

Iranians gathered in central Tehran on Monday night to celebrate the attack, images on state TV showed, with some waving the flag of the Islamic republic and chanting "Death to America".

Earlier in the day, Qatar had announced the temporary closure of its airspace in light of "developments in the region", while foreign embassies there including that of the United States had warned their citizens to shelter in place.

After the attack, Qatar said "the security situation in the country is stable, and there is no cause for concern".

- Tehran strikes -

Just as Iran was announcing the new attacks, blasts were heard in the north of Tehran, according to an AFP journalist, who reported yellow flashes typical of Iranian air defences in the sky over the capital shortly before 9:00 pm (1730 GMT).

Earlier in the day Israel reported carrying out what it said were its most powerful strikes yet on Tehran.

Iran, in turn, fired missile barrages at Israel.

Israeli Defence Minister Israel Katz said the military hit sites in Tehran including Evin prison, which Katz said "holds political prisoners and regime opponents", as well as command centres for the domestic Basij paramilitary and the Revolutionary Guards.

Iranian media and the Israeli military said Israel also struck Fordo on Monday "in order to obstruct access routes" to the site.

Israeli strikes on Iran have killed more than 400 people, Iran's health ministry has said. Iran's attacks on Israel have killed 24 people, according to official figures.

China urged both Iran and Israel to prevent the conflict from spilling over, warning of potential economic fallout.

- Oil prices fall -

Oil prices sank more than six percent on Monday after the attack.

Around 1815 GMT, futures for West Texas Intermediate fell 6.5 percent to $69.96 a barrel, while Brent oil futures dropped 6.4 percent to $72.07 a barrel, its lowest level in 10 days.

John Kilduff of Again Capital described the Iranian action as "somewhat measured".

"This is a face-saving measure by the Iranians and hopefully the diplomatic off-ramp will be taken," Kilduff said.

On Sunday, after the Pentagon stressed the goal of US intervention was not to topple the Iranian government, Trump had openly toyed with the idea.

"If the current Iranian Regime is unable to MAKE IRAN GREAT AGAIN, why wouldn't there be a Regime change???" Trump posted on his Truth Social platform.

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