CANBERRA, Australia -- An Australian boy who was photographed holding the severed head of a Syrian soldier could reportedly return to Australia with his mother and siblings, prompting the prime minister to warn Wednesday that children as well as adults who break terrorism laws face prosecution.

Sydney-born convicted terrorist Khaled Sharrouf horrified the world last year by posting on his Twitter account from Syria a photograph of his 7-year-old son clutching the severed head.

U.S. Secretary of State John Kerry described the image as "one of the most disturbing, stomach-turning, grotesque photographs ever displayed."

Fairfax Media newspapers reported Wednesday that the Australian family of Sharrouf's Muslim convert wife, Tara Nettleton, was trying to help her and her five children return to Sydney.

Asked about the family, Australian Prime Minister Tony Abbott said if the children had committed a crime, they would be treated by the Australian courts the same way as other juvenile offenders.

"But the point I want to stress is that criminals will be punished whether they're young, whether they're old, whether they're male, whether they're female, whether they're criminals abroad or criminals at home," Abbott told reporters.

"Criminals will be punished and to participate in the kind of barbarism that we have seen so often in the Middle East is just wrong. It's morally wrong and it's a crime under Australian law and it will be punished," he said.

There is no evidence that Sharoouf, who slipped out of Australia in late 2013 using his brother's passport because his own had been cancelled, wanted to return to Australia, the newspapers reported. Police have confirmed he faces an arrest warrant in Australia on terrorism offences.

Nettelton later brought their three young boys and two teenage daughters to Syria, flying with return tickets via Malaysia to hide from Sydney Airport officials their intended destination.

The family's current whereabouts are not clear.

Australia used controversial new counterterrorism laws in December to make even visiting the Islamic Statement movement's stronghold of al-Raqqa province in Syria a criminal offence punishable by 10 years in prison.

Australia has cancelled the passports of scores of suspected terrorists, preventing would-be jihadis from leaving the country and stranding foreign fighters overseas.

Australia also plans to pass a law soon to give the government the power to strip citizenship from dual nationals who are suspected terrorists even if they are not convicted of a crime.

But Immigration Minister Peter Dutton said Wednesday that children of terrorists would be treated as a special case. The children could become wards of the state if their mother was imprisoned.

Sharrouf was among nine Muslim men accused in 2007 of stockpiling bomb-making materials and plotting terrorist attacks in Sydney and Melbourne, Australia's largest cities.

He pleaded guilty to terrorism offences in 2009 and served less than four years in prison.