One woman has been charged with joining ISIS and two others are expected to be accused of crimes against humanity linked to slavery, following their long-speculated return to Australia.

Police arrested two women, aged 53 and 31, when they landed at Melbourne Airport tonight and a third – 32-year-old Janai Safar, who was travelling with her nine-year-old son – in Sydney.

Just after 11pm, the AFP, NSW Police Force, ASIO and NSW Crime Commission announced the 32-year-old woman had been charged for allegedly entering and remaining in a declared conflict zone and joining ISIS.

Janai Safar arrives at Mascot Police Station. (Nine)

AFP Assistant Commissioner Counter Terrorism Stephen Nutt said the older woman was expected to be charged with four crimes against humanity of enslavement, possessing a slave, and using and engaging in slave trading, while the 31-year-old would be accused of enslavement and using a slave.

They all carry 25-year jail terms if proven.

The return of four women commonly described as “ISIS brides” and nine children, who had spent years living in Syria’s Al-Roj refugee camp, sparked major police operations at Melbourne and Sydney airports tonight, following weeks of heated on-and-off political debate.

The cohort who followed their ISIS partners to Syria more than a decade ago have faced a long journey in their return to Australia.

The women and their children have been held in refugee camps in north-eastern Syria for years, following the collapse of ISIS, and recently failed in an attempt to leave the camp for Australia earlier this year.

The families left the notorious Al-Roj camp for the Syrian capital in their second bid to return to Australia nearly two weeks ago, and had been waiting in limbo in Damascus since.

AFP Assistant Commissioner Counter Terrorism Stephen Nutt addresses the media. (9News)

On Wednesday, the Australian government confirmed the group had booked flights to Australia.

The women were looking forward to drinking a latte on Melbourne’s Collins Street, according to an ABC journalist on the flight from Doha who spoke to the women before boarding.

Some of the children reportedly have Australian accents, despite being born in Syria and never setting foot in Australia.

The Australian government insists it has not helped the group return to Australia.

A woman associated with Islamic State is shielded as she arrives at Melbourne Airport. (Getty)

Former immigration department deputy secretary Abul Rizvi said there was no doubt the government had been “involved in the sense that they’ve had people monitoring these groups”.

“Moreover, when they applied for passports, those passports would have been processed … so in that sense the government was involved,” he said.

“The distinction I think the government is making is they were not involved in the repatriation. They did not arrange or pay for these people to return.”

Rizvi said the return would “set a precedent” for the other women and children connected to ISIS fighters to follow their path.

Janai Safar was travelling with her nine-year-old son. (Nine)

“They will seek to try to return, and we’ll have to wait and see how that plays out,” he said.

Nutt wouldn’t comment on how many other women the AFP was expecting to return home.

He wouldn’t say whether the fourth woman who arrived in Australia tonight would face charges, or detail any plans for monitoring of the children.

After the 32-year-old was charged, Nutt said Joint Counter Terrorism Teams investigated all Australians who went to declared conflict zones and promised to put anyone alleged to have committed a criminal offence before the courts.

“This remains an active investigation into very serious allegations”.

The opposition had called for the government to cancel their travel documents or make a temporary exclusion order to keep the entire cohort out of the country but the government argued that as Australian citizens they were allowed to travel.

Prime Minister Anthony Albanese and other ministers repeatedly urged the women not to return to Australia.

A group of supporters shield recently arrived people with links to Islamic State as they arrive at Melbourne Airport. (Getty)

Nutt tonight said whether or not the alleged crimes rose to a level that would justify a temporary exclusion order was a matter for the Home Affairs Department.

Nationals Senator Bridget McKenzie and independent Senator David Pocock provided an example of the debate this morning on Today.

McKenzie said there were “serious concerns” around the group of women, and claimed the children were “already radicalised”.

“I want to know why the government hasn’t cancelled their travel documents under national security grounds,” she said.

A group of supporters shield recently arrived people with links to Islamic State as they move into a bus outside Melbourne Airport. (Getty)

Pocock pointed out the women were Australian citizens, but that nonetheless the public expected “the full force of the law” to be enacted but argued “Australian children deserve a second chance”.

He said it was preferable that the group be in Australia where they could face legal repercussions and de-radicalisation programs, but McKenzie claimed the programs had a low success rate.

“I think the thing we really have to distinguish between, is grown adults, and children who have had no say in going overseas,” Pocock said.

The 32-year-old is due to face Downing Centre Local Court tomorrow on charges of entering, or remaining in, declared areas and being a member of a terrorist organisation.

Both offences carry maximum sentences of 10 years if proven.

The women arrested tonight in Melbourne could face court as early as tomorrow if they are charged tonight.