The ABC has learned that a Brisbane woman facing charges for supporting terrorism is married to an Australian believed to be fighting in Syria who apparently openly supports one of the most brutal militant groups involved in the civil war.

Fatima Elomar was travelling with her four children when she was stopped by police on May 3.

Her lawyer insisted she was heading overseas for a family reunion. Police reportedly seized a sum of cash and military fatigues.

The 29-year-old was taken to Mascot Police Station where she was charged under the Crimes (Foreign Incursions and Recruitment) Act 1978 with supporting incursions into a foreign state with the intention of engaging in hostile activities.

Mystery has surrounded the identity of both Fatima Elomar and her husband Mohamed Elomar, until now.

The ABC can reveal that court records released online show that Fatima Elomar is due to appear in Downing Centre Local Court on June 2.

Authorities have confirmed to the ABC that she is the wife of Mohamed Elomar, who is believed to have left Sydney for Syria last November.

A number of pictures of Mohamed Elomar appear on a Facebook page under the alias Abuhafs al Australi. These include photographs of him in military clothing, brandishing a weapon, and others of his and Fatima's four children.

On a Facebook page, Abuhafs al Australi openly declared his loyalty to ISIS - a hyper-militant terrorist group known in the West as the Islamic State of Iraq and the Levant or the Islamic State of Iraq and Syria.

"Whosoever dies without participating in an expedition (jihad) nor having the intention to do so, dies on a branch of hypocrisy," said one entry on the Abuhafs Facebook page.

ISIS too extreme for Al Qaeda

ISIS is so extreme it has been rejected even by Al Qaeda. ISIS is seen as the main stumbling block for a settlement in the Syrian civil war.

Terrorism expert Professor Greg Barton from Monash University says, if the allegations against him are true, Mr Elomar may be engaged in more than activism.

"Mohamed Elomar is one guy who slipped through late last year when authorities would have stopped him if they could have," he said.

"It is a worry for him and a worry if he comes back - the sort of radicalisation process that he has experienced, the skills that he has learnt, a new phase of global terrorism that we haven't seen the like of before."

Video clips uploaded on Abuhafs al Australi's Facebook site show militant jihadists in a jubilant mood.

There are several grisly snapshots of corpses identified as enemies of ISIS, along with derogatory remarks that appear to mock the dead.

Above one body is the remark "Maliki soldiers need to wear nappies before visiting ISIS". It is a reference to Nuri al Maliki, the Iraqi prime minister whose forces are waging war on ISIS in Iraq.

"It [ISIS] is a vicious, brutal group led by a man named Abu Bakar al Baghdadi," Professor Barton said.

"He broke several hundred terrorists out of prisons across Iraq partly to fight in Iraq but also to fight in Syria."

It's not adventure terrorism, expert says

Although ISIS has so far failed to take over the main Al Qaeda group in Syria, the group is said by some analysts to be the most powerful rebel force engaged in the north of the country.

It has imposed strict rules in cities that it occupies, from the enforcement of the veil to a more sinister and rough form of justice.

In the city of Raqqah, accounts have emerged of men being snatched from the street, tortured and summarily executed.

Professor Barton says it is a frontier in a war that is not far away.

"There are very few barriers to entry. It is cheap to get to Turkey. It is easy to get across [to Syria], or at least it has been," he said.

"You can come and go if that's what you want to do. It is a conflict that has transformed international jihadi conflict in a way that no other conflict has.

"It might look like adventure terrorism, but it is very hardcore stuff."

Mohamed Elomar's uncle, also named Mohamed, was one of 18 people jailed for a plot to blow up targets in Sydney and Melbourne.

His brother Ahmed is awaiting sentence for his role in the Hyde Park riot two years ago against a film that mocked Islam.

Through a lawyer, the Elomar family strongly denied Mohamed Elomar was in Syria or neighbouring Turkey.

They insist someone else is operating the Abuhafs Facebook page that carries images of their son and brother.

Do you know more? Email investigations@abc.net.au