The Australian government is trying to confirm reports that two of its citizens who went to fight for Islamic State have been killed in Iraq.
Australian media reported that Khaled Sharrouf and Mohamed Elomar were killed while fighting in Iraq.
The two came to public notice last year after pictures of severed heads were posted on their social media accounts.
Foreign Minister Julie Bishop said on Tuesday the government was close to verifying one of the deaths.
"The likelihood of verification in relation to Mr Elomar is probably imminent," she said.
"However, in relation to Mr Sharrouf, we're still seeking to verify the reports."
The Australian Broadcasting Corp (ABC) reported that sources close to the families of the two men said they were recently killed either during fighting or by a drone strike.
Ms Bishop on Tuesday said that Elomar was believed to be in Mosul, and that there had been a number of air strikes there in recent days.
But she added: "Given the security situation in Iraq, it's difficult for our authorities to gain the kind of information that would be required to verify these reports."
The two men had travelled to Syria and then Iraq in 2013. Last year they posted images of severed Syrian soldier heads on social media. Sharrouf also allowed his seven-year old son to be photographed holding up a severed head.
At some stage, Sharrouf's wife and children joined him in Syria, and his teenage daughter reportedly married Mr Elomar.
The Australian government had cancelled the two men's passports and last year police warrants were issued for both men.
Sharrouf, who was on a security watch list, used his brother's passport to leave Australia.
Sharrouf was sentenced to four years in prison in 2009 for his role in a plot involving targets in Sydney and Melbourne.
He had been arrested with several others in 2005 in what was then the largest anti-terror raid in Australian history, code named Operation Pendennis by police.
Sharrouf's wife and their five children had reportedly wanted to return to Australia.
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