The repatriation, which has led to criticism from the Liberal-National opposition, is part of a programme of taking back from Syria dozens of Australian women and children who are relatives of dead or jailed ISIS terrorists.
Australia first rescued eight children and grandchildren of two dead ISIS extremists from a Syrian refugee camp in 2019, but has held off repatriating others until now.
“The decision to repatriate these women and their children was informed by individual assessments following detailed work by national security agencies,” Ms O'Neil said in a statement.
The women and children left the Al Roj refugee camp in northern Syria on Thursday afternoon and crossed the border into Iraq to board a flight home, the Sydney Morning Herald and state broadcaster ABC reported on Friday.
Ms O'Neil said at all times the focus has been on the safety and security of “all Australians” as well as those involved in the repatriation, with the government having “carefully considered the range of security, community and welfare factors in making the decision to repatriate”.
The repatriation followed similar moves by the US, Italy, Germany, France, the Netherlands, Belgium, Britain and Canada, Ms O'Neil said.
She said investigations into allegations of illegal activity by state and federal law enforcement authorities would continue. Local media reported some women may be charged with terrorism offences or for entering Syria illegally.
“Any identified offences may lead to law enforcement action being taken,” Ms O'Neil said, adding that New South Wales was providing “extensive support services” to assist the group to reintegrate into Australia.
Opposition Leader Peter Dutton said the move was not in Australia's best interest and that the women have mixed with “people who hate our country, hate our way of life”.
Prime Minister Anthony Albanese has said the government would continue to act on national security advice on the issue.