Updated

The alleged Sydney ringleader of a criminal network that sends Australians to fight in Syria has been arrested, police said Tuesday.

Police estimate that about 100 Australian residents and citizens have traveled to Syria to fight in contravention of Australian law, some taking up arms with terrorist-linked militias.

Two Sydney men became the first suspects to be arrested by a four-month-old joint federal and state police counter-terrorism investigation into Australian citizens attempting to travel to Syrian to fight in the civil war, Australian Federal Police Deputy Commissioner Peter Drennan said.

"We will allege that one of the men is responsible for organizing travel, arranging overseas contacts and facilitating travel into Syria for Australian citizens to fight on the front line," Drennan said.

The 39-year-old suspected ringleader and a 23-year-old suspected recruit are to appear in Sydney courts Tuesday charged under the Crimes (Foreign Incursions and Recruitment) Act. The act outlaws Australian residents or citizens traveling overseas to fight or recruiting others to fight. It carries a maximum 10-year prison sentence.

New South Wales state Deputy Police Commissioner Catherine Burn said the network had already sent six Australians to Syria to fight.

"We have identified who we believe is the principle person involved in the facilitation network of sending people over to Syria to engage in conflict," she said.

Drennan said the difficulty in gathering evidence from Syria had prevented police making more arrests.

The Syrian war has attracted Australian civilian combatants like no other conflict in recent decades. Many are from Lebanese backgrounds. Security officials fear that many will become radicalized by the war and could pose a terrorist threat when they return to Australia.