The death of Neil Prakash is considered significant by Australian and American authorities because of his highly prominent and influential role as a senior recruiter for the jihadist group.
Attorney General George Brandis said Washington had told Canberra that Prakash was killed in Mosul, Iraq, on April 29. "Neil Prakash was a prominent ISIL member and a senior terrorist recruiter and attack facilitator," he said in a joint statement with Defence Minister Marise Payne, using an acronym for IS.
"Prakash has been linked to several Australia-based attack plans and calls for lone-wolf attacks against the United States. He is considered to be Australia's most prominent ISIL recruiter."
American authorities also told the government that Australian woman Shadi Jabar Khalil Mohammad died in a similar air strike near the Syrian city of Al Bab on April 22, along with her Sudanese husband.
"Mohammad and her husband, Abu Sa'ad al-Sudani, were both active recruiters of foreign fighters on behalf of ISIL, and had been inspiring attacks against Western interests," said Brandis. She was the sister of Farhad Jabar, a 15-year-old who shot dead police employee Curtis Cheng in Sydney last October.
The teenager was killed in gunfire shortly afterwards. Prakash, who left Australia in 2013 and was known as Abu Khaled al-Cambodi, was linked to an alleged terror plot on Anzac Day last year, when Australia honours its war dead.
He has also appeared in IS propaganda videos, including one last year calling for attacks on Australia. "His death disrupts and degrades ISIL's ability to recruit vulnerable people in our community to conduct terrorist acts," Brandis added.
Australia has long been concerned about home-grown extremism and raised the terror threat alert level to high in September 2014. At least six attacks have been foiled on Australian soil over the past 18 months, according to the government. But several have taken place, including the terror-linked murder of Cheng.