The Pentagon is playing down concerns that the attack on Iran risked plunging the US into a new, open-ended conflict in the Middle East, even as officials declined to give a timeline.

Israel launched new air strikes targeting Iran and expanded its assault to include attacks on Hezbollah in Lebanon, as Tehran said it launched a new wave of missiles that had "opened the great gates of fire" on Israel.

Demonstrations against the US-Israeli bombing campaign in Iran turned violent in Pakistan and Iraq, while elsewhere Iranian exiles took to the streets to celebrate the death of Supreme Leader Ayatollah Ali Khamenei.

Australia's Prime Minister says the arrest of a Western Australian man over an alleged terror plot targeting mosques, police and a parliament building was "deeply shocking".

"You will have hundreds of thousands of people being stuck in wrong parts of the world without any certainty as to when they can move."