By Dominic Giannini and Tess Ikonomou in Canberra

More than 100,000 Australians are in the Middle East as the US-Israel war on Iran continues, and the federal government warns stranded citizens commercial flights will be the fastest way to get home.

The US and Israel launched air strikes on Iran, killing its leader Ayatollah Ali Khamenei and more than 40 senior officials, as the two nations push for regime change.

US President Donald Trump told the Daily Mail the war in Iran would take  “four weeks or so”.

Three American troops have been killed in the conflict and five others have been wounded, the Pentagon confirmed.

Foreign Minister Penny Wong said there were about 115,000 Australians in the region as airspaces remain closed.

“The fastest way to get people home would be if commercial flights recommence,” she said on Monday.

“We are always looking at home (how) we might support Australians … and airspace is not open.

“Whether or not it is an Australian flight or a commercial flight, the flights are not able to occur.”

Senator Wong said a portal will be available to people in Iran, Israel, Qatar and the UAE to give them the most up to date information.

Defence Minister Richard Marles said US facilities in Australia were not used in the attack, describing Iran’s leadership as “abhorrent”.

“We do support the action that the United States has taken, and we very much stand with the Iranian people in this moment,” he told ABC radio.

Asked if the attacks were deemed legal under international law, Mr Marles replied: “Ultimately, the legality of these measures is a matter for both the United States and Israel to go through.”

Iranians in Australia took to the streets to celebrate the strikes on Tehran, marking them as the beginning of the end for the brutal regime.

Rallies took place in Sydney, Melbourne and outside the former Iranian embassy in Canberra, where members of the community sprayed champagne, cheered and danced.

Some smaller anti-war demonstrations also broke out, with groups such as the Jewish Council of Australia condemning Prime Minister Anthony Albanese’s endorsement of the US strikes.

Australian Travel Industry Association chief executive Dean Long warned travellers transiting through the Gulf to expect delays and rerouting “for the foreseeable future”.

He warned Australians not to cancel flights, even to nations upgraded to do-not-travel warnings.

“Let the airline or tour operator make that call – if they cannot provide the service because it is unsafe, your rights are much better protected,” Mr Long said.