US President Donald Trump has raised the spectre of regime change in Iran, posting “MAKE IRAN GREAT AGAIN” as the world braces for Tehran’s response to weekend strikes.

The US attacked key Iranian nuclear sites on Sunday, joining Israel in the biggest Western military action against the Islamic Republic since its 1979 revolution.

A day after the US sent 13,600-kilogram bunker-buster bombs crashing into the mountain above Iran’s Fordow nuclear site, Tehran vowed to defend itself at all costs, American leaders urged Tehran to stand down, and pockets of anti-war protesters began taking to the streets in US cities.

“It’s not politically correct to use the term, ‘Regime Change,’ but if the current Iranian Regime is unable to MAKE IRAN GREAT AGAIN, why wouldn’t there be a Regime change??? MIGA!!!” Trump wrote in a post on Truth Social wrote.

In a follow-up post, Trump said “monumental damage” had been done to Iran’s nuclear sites in the weekend raids.

“Obliteration is an accurate term!” he said, citing a satellite image he did not share.

“The biggest damage took place far below ground level. Bullseye!!!”

Iran and Israel continued to trade volleys of missile attacks on Monday, with an explosion in western Iran claiming the lives of half a dozen military personnel, according to an Iranian media outlet.

Earlier, Iran fired missiles that wounded scores of people and flattened buildings in Tel Aviv.

On Monday, in the first sign of retaliation for the US attack, Iran’s parliament voted to close the Strait of Hormuz, which about a quarter of the world’s oil transits through. That has prompted oil fears prices could push to $US100 a barrel or more.

US Secretary of State Marco Rubio said earlier shutting the strait would be a “suicidal” move for Iran. He also urged China — Iran’s most crucial oil customer — to encourage against shutting it down.

“I encourage the Chinese government in Beijing to call them about that, because they heavily depend on the Straits of Hormuz for their oil,” Rubio said on Fox News’s Sunday Morning Futures with Maria Bartiromo.

He told another talk show that the US had “other targets we can hit, but we achieved our objective”.

“There are no planned military operations right now against Iran,” said, “unless they mess around”.

Iran’s Supreme National Security Council will ultimately decide on the move.

Earlier, Tehran said Trump had “betrayed” Iran, as well as Americans with its strikes, and threatened “everlasting consequences”.

Late on Sunday, the US State Department issued a worldwide security alert for Americans.

“There is the potential for demonstrations against US citizens and interests abroad. The Department of State advises US citizens worldwide to exercise increased caution,” it said.

Speaking in Istanbul, Iranian Foreign Minister Abbas Araqchi said his country would consider all possible responses. There would be no return to diplomacy until it had retaliated, he said.

“The US showed they have no respect for international law. They only understand the language of threat and force,” he said.

Ali Shamkhani, an adviser to Iran’s Supreme Leader Ayatollah Ali Khamenei, said on X, formerly Twitter, that the initiative was “now with the side that plays smart, avoids blind strikes. Surprises will continue!”.

The UN Security Council met on Sunday to discuss strikes on Iran’s nuclear sites as Russia, China and Pakistan proposed the 15-member body adopt a resolution calling for an immediate and unconditional ceasefire in the Middle East.

UN Secretary-General Antonio Guterres said earlier the US bombings in Iran marked a perilous turn in the region. He urged a halt to fighting and return to negotiations over Iran’s nuclear program.

In Israel, Prime Minister Benjamin Netanyahu said the nation was close to meeting its goals of removing the threats of ballistic missiles and the nuclear program in Iran.

Satellite damage showing damage to Iran’s Fordow underground nuclear site. Photo: AAP

Australia backs US strike

Prime Minister Anthony Albanese has backed US strikes on Iranian nuclear facilities, while also urging a de-escalation of the conflict in the Middle East.

In his first public comments since the US launched strikes on the facilities in Fordow, Isfahan and Natanz, Albanese said on Monday a larger war must be avoided.

“The world has long agreed that Iran cannot be allowed to get a nuclear weapon and we support action to prevent that,” he said in Canberra.

“We don’t want escalation and a full-scale war. We continue to call for dialogue and for diplomacy.

“Australia called upon Iran to come to the table and abandon any nuclear weapons program.

“Iran didn’t come to the table, just as it has repeatedly failed to comply with its international obligations.”

The comments came after Albanese convened a National Security Committee meeting in Canberra on Monday.

Earlier, Foreign Minister Penny Wong said Washington had made no requests of Australia.

But she would not say if the joint US intelligence surveillance base, Pine Gap, in the Northern Territory had played a role in the operation.

Wong said the number of Australians who had registered for help to leave the region had jumped to about 2900 in Iran and 1300 in Israel.

-with AAP