A worrying number of Australian women are heading to Iraq and Syria to become so-called Islamic State group "jihadi brides", Foreign Minister Julie Bishop said Thursday, warning against notions of a "romantic adventure".

At least 110 Australians have left to fight alongside militants in the Middle East and security officials said between 30 and 40 women were among them or were actively supporting the group in Australia.

"Sadly we are seeing a younger cohort seeking to join the conflict in Syria and Iraq and an increasing number of young females," Bishop said, responding to the high-profile case this week of three British teenage girls heading to Syria.

"This defies logic. Family and friends need to reach out to young people at risk before it's too late."

She cited the case of 22-year-old Amira Karroum who left her Sydney home just before Christmas and died in fighting in Syria.

"Her death was not martyrdom, it was a tragic senseless loss," said Bishop.

She added that many women heading to conflict zones were either attracted to male foreign terrorist fighters, were accompanying their partner, or actually looking for a husband and being told online they could find one in Syria and Iraq.

Bishop warned they faced a brutal regime that treated women appallingly.

"This is a terrorist organisation that has an appalling track record when it comes to women," she told ABC radio.

"They actually have online instructions on how to treat a sex slave. They encourage sexual assault on children who haven't even reached puberty.

"So their attitude towards women is utterly appalling and so young women shouldn't be led to believe that there's some romantic adventure attached to supporting Daesh (Islamic State) and similar terrorist organisations."

An estimated 550 women from across Europe have also travelled to join the jihadists and Bishop said Australia was working with Muslim communities to highlight the risks.

"We have a number of community initiatives and programmes, working with local communities, working with schools, working with families," she said.

"Our initiatives in tackling the spread of online extremist content on websites is also part of that, working with local mosques, working with community groups."

Her comments came as an Australian man who travelled to Syria to battle militants was reportedly killed -- the first Westerner to die fighting alongside the Kurds.

"An Australian man was killed in an assault on Tuesday by the Islamic State against a position of the Kurdish People's Protection Units (YPG) near Tal Hamis in Hasakeh province," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

Australia's foreign affairs department said it was aware of the reports but its "capacity to confirm reports of deaths in either Syria or Iraq is extremely limited".

"Australians who become involved in overseas conflicts are putting their own lives in mortal danger," it added.