Ms Jabar was with her Sudanese husband, Abu Sa'ad al-Sudani, who was also killed. Both were regarded as active recruiters for the Islamic State group.

She joins the most senior Australian fighting with the Islamic State terror group, Neil Prakash, to have been killed in US air strikes. Ms Jabar was killed in a separate strike a week earlier, said US officials who advised of her death.

Neil Prakash, also killed in US air strike.

Prakash, 24, who was at the centre of a web of highly active recruitment that inspired terrorism plots in Australia and drove adherents to join the group in the Middle East, was directly targeted in the strike in Iraq by a US fighter plane last Friday, the Australian government was also told by US officials.

Prakash, originally from Melbourne, was killed  with up to 10 other Islamic State jihadists when the building they were in was struck in Mosul, the group's defacto capital in Iraq.

Prakash himself was a key target. His death brings to an end more than a year in which he was a key figure in pushing Islamic State's ideology into Australia.

He was a high-value target because of his prominence as a recruiter, not just for his native Australia but in other countries as well. He had starred in one of the jihadist group's glossy promotional videos and was linked to multiple extremist plots in Australia but also to calls for lone-wolf attacks in the United States.

He was regarded as an enemy combatant under international law and is understood to have been on a so-called "kill list".

It is not clear whether Australian authorities played any role in the targeting or intelligence collection that led to either of the strikes, but Australian defence and intelligence officials work closely with US counterparts.

Prakash's death is particularly significant because, while he filled the shoes of a previous successful recruiter Mohammad Ali Baryalei, there was no obvious successor to Prakash.

Greg Barton, a terrorism expert at Deakin University, said Prakash was the last known, high-profile link between the Syria-Iraq battlefield and the enduring extremist networks in Sydney and Melbourne.

He is believed to have been involved in influencing  the recent alleged Anzac Day plot in Sydney and the alleged Mother's Day pipe bomb plot in Melbourne last year. He also helped radicalise Numan Haider, who was shot dead in Melbourne after attacking two policemen with a knife.

"His death is very welcome in that he's the last prominent Australian that we're aware of who served as a key link with friends back in Australia," Professor Barton said.

"It doesn't mean the end of these exchanges, but it certainly marks the closing of the first chapter," he said.

He was linked to  the al Risalah group in Sydney and the al Furqan centre in Melbourne, "including, sadly, Numan Haider", Professor Barton said.

The fact he was killed in Iraq is significant because he spent most of his time in the group's Syrian stronghold of al-Raqqa.

His movement underscores the solidity of the large territory the Islamic State still holds spanning Syria and Iraq, despite significant territorial losses they suffered.

Prakash had long been extremely active on social media pushing his messages but recently he had gone quiet, apparently out of fear that his location would be picked up.

A source said his death was "a very, very significant disruption to recruitment" because he was "a very prolific recruiter of vulnerable young people".