An Australian woman has been charged with supporting "hostile activities" in a foreign country after she was arrested trying to board a flight from Sydney with her four young children.

Unconfirmed reports said the woman, 29, was carrying money and equipment, including camouflage clothing, for her husband, who is alleged to be fighting in Syria.

"This arrest relates to Operation Duntulm that has a focus on foreign incursion offences," police said in a statement, the AFP news agency reported.

"She was charged with supporting incursions into a foreign state with the intention of engaging in hostile activities"

The woman, who was arrested on Saturday evening, was granted conditional bail and will appear at a court in Sydey on June 2.

Officials say more than 100 Australian citizens have travelled to fight alongside rebels in Syria, with the government earlier this year expressing concern after several reported deaths.

Attorney General George Brandis has said he is worried about the potential security threat posed by Australians returning home from fighting in Syria.

Under Australian law, it is an offence to travel to a foreign state or help someone to travel with the intention of engaging in combat. Legislation also prevents providing or receiving training abroad.

Hundreds of citizens from Western countries are believed to have travelled to Syria to join rebels in their fight against the Assad government.

The government of Belgium estimates that more than 2,000 volunteers have travelled from the European Union.

Source: Agencies