Australian Muslim groups have condemned the use of slaves, calling it barbaric and completely out of line with Islam.
The condemnation came amid claims Australian jihadists Mohamed Elomar and Khaled Sharrouf, who are fighting alongside Islamic State in Iraq and Syria, have enslaved women from the Yazidi religious minority in northern Iraq.
Of the 80 or so suspected Australian jihadists in the region, they are the best known, and their activities have caused a great deal of concern for local Muslims.
News they could be holding slaves has generated disgust among senior members of the Islamic community in Australia who have warned that extra funding needs to be put into programs to prevent young Muslims from being radicalised.
Prominent Muslim community spokesman Keysar Trad said the claims the men are holding slaves is concerning.
"This is certainly very, very disturbing news, and our sympathies are with the victims. We really feel for those girls and for their loved ones," he said.
Joumanah El-Matrah, who heads the Muslim Women's Centre for Human Rights, is also appalled.
"From the Islamic perspective, Islam does certainly not allow for the enslavement of other human beings, much less the selling of them," he said.
"One of the positive things about Islam is that it actually works to eradicate the enslavement, particularly of women, which was quite common in Islam's early history.
El-Matrah baffled by Australian militant motives
Elomar's postings on social media indicate he is a popular and influential figure among Australians who turn up to fight for Islamic State.
Recent postings show he was in contact with Mahmoud Abdullatif, a Melbourne man who has reportedly been killed in combat in Syria.
Elomar also recently posted a photo of a Yazidi child holding a gun. The picture is captioned: "he is starting to get the idea that ISIS is a way of life."
Islamic State's brutally and extreme interpretation of Islam is unparalleled.
Mr El-Matrah finds it baffling how anybody who has had the opportunities Australia provides could follow it.
"It's really quite difficult to understand how two young Australian men, having grown up in this country, can actually take those views of other human beings, and then label it as Islamic," he said.
"I think that many community leaders and other professionals in the area are still trying to understand exactly how these young men have arrived at the situation that they're in."
Community-based programs needed to stop radicalisation
After recent briefings with US security officials, Foreign Minister Julie Bishop said she was even more troubled by the threat of foreign fighters.
Many Muslims say more needs to be done to prevent young people from becoming radicalised in Australia.
Last year, the Government allocated $13.4 million to fund programs aimed at preventing young Australians becoming involved with extremist groups.
But some Muslim leaders say the community is yet to see any of that money in action.
Mr El-Matrah warned the threat of radicalisation would grow unless it was tackled at a community level.
"Unfortunately, in the last two or three years, we've moved away from community based approach, and getting the community itself to work on issues of radicalisation," he said.
"Communities are being quite open to doing that work and there's been some very solid work to date."
"Unfortunately, the Government has withdrawn resources from that area, which I think is a mistake, and is contrary to what is happening in almost every other part of the world when it comes to radicalisation - from Muslim countries that may be labelled developing nations, to places like the US and the UK, where community approaches seem to be now the most important approach to take."