A mother of four has been arrested at Sydney Airport and charged during a police counterterrorism operation.

Officers from the joint counterterrorism team stopped a woman trying to board an international flight with her four young children on Saturday evening.

Police say the 29-year-old Brisbane woman was arrested and taken to Mascot Police Station in Sydney's south, where she was charged with supporting incursions into a foreign state with the intention of engaging in hostile activities.

The arrest relates to Operation Duntulum, which is targeting foreign incursion offences.

Police will not say where the woman is from or where she was intending to travel.

Three properties were also searched as part of the operation; two in Sydney and one in Brisbane.

The woman was released from custody but must abide by strict bail conditions.

She will face Sydney's Downing Centre Local Court on Monday, June 2.

ASIO has previously confirmed that almost 100 Australians have travelled to Syria to fight in the ongoing conflict since it began, with a number of Australians being killed by rebels.

Last year, the Australian Federal Police arrested two Sydney men, one of whom allegedly tried to leave Australia to go fight on the frontline in against the Assad regime.

Federal Attorney-General George Brandis says such incidents are a reminder that if any Australian travels to Syria to participate in the conflict they would be breaking the law.

"It is incumbent on me as the Attorney-General to make it loud and clear to Australians who may be minded to travel to Syria to participate in that conflict that they expose themselves to risk if they participate - they are committing a crime," he said.

"And if it's established that they have done so they will be prosecuted. This is not something that Australian citizens should be involved in."