CANBERRA - The wife of Australian Islamic State fighter Khaled Sharrouf will face "the full severity of Australian law" if she returns from Syria with her five children, Australia's Prime Minister said on Wednesday.

Sharrouf hit headlines around the world last year after he tweeted a photograph of his son holding a severed head in Syria. It came shortly after a photograph was released where Sharrouf and his three sons, dressed in camouflage and wielding weapons, posed in front of an Islamic State flag.

There is no indication Sharrouf, for whom an Australia arrest warrant remains outstanding, wants to return but inquires have been made on behalf of Sharrouf's wife, Tara Nettleton, according to Fairfax Media.

Nettleton's mother, Karen, is believed to have made a trip to Malaysia recently in an effort to arrange a return for Nettleton and her five children.

Prime Minister Tony Abbott told reporters on Wednesday that Nettleton would receive no special treatment if she returned home.

"Crime is crime is crime," he said. "Criminals will face the full severity of Australian law and it is a crime, a very serious crime under Australian law, for people to go abroad and fight or assist terrorist organizations."

Discussing the possibility of a returned fighter being used as a mentor to stop others to take up arms for Islamic State, Abbott said that could only happen after punishment.

"I'm absolutely delighted when a criminal comes out of jail, reformed and rehabilitated, for that criminal or former criminal to go and spread a message of obeying the law to others," he said.

"But I'm afraid you don't get off scot-free just because you say 'oh I've seen the error of my ways'."

When asked how the children of Nettleton will be cared for, Abbott said authorities would follow the regular procedure.

"These are not the first criminals to have had children," he said. "I mean, there are criminals who go to jail all the time and they have children, and the children of these particular criminals will be dealt with in the same way that the children of criminals are normally dealt with."

Opposition Leader Bill Shorten likened the children's case to child abuse, saying they should never have been taken there and would be "scarred" from the experience.

He said he would seek a briefing from the government's security agencies but supported foreign fighters facing the full force of the law.