AUSTRALIAN security agencies believe more than 100 Australians have joined the civil war in Syria, sparking fears the conflict could produce a wave of home-grown jihadists hardened with combat skills and training.
The concerns come amid fears that hundreds of thousands of dollars a month are leaving Australia, bound for the conflict zone, with some flowing to rebel jihadists.
The Australian Federal Police's deputy commissioner in charge of national security, Peter Drennan, confirmed the Syrian conflict had resulted in a spike in the number of Australians travelling overseas to fight.
"For several years we have seen individuals who plan to, or (do), travel overseas to train and fight as terrorists," Mr Drennan told The Weekend Australian.
"These have been relatively few, but even one is a concern. With increased areas of conflict in the Middle East and North Africa, we have seen an increase in the numbers, albeit still low, of Australians travelling overseas to be involved in these conflicts. The most recent conflict attracting Australians is Syria."
He said Australians travelling to foreign hotspots to engage in fighting represented an evolution in the terrorism threat here in Australia.
"These individuals then return with training in the use of weapons and explosives and experience fighting in armed conflict," Mr Drennan said.
"The individuals could well use these skills and knowledge for terrorism in Australia."
There are concerns the war, which has pitted Syria's Sunni majority against the minority Alawite regime of Bashar al-Assad, could stoke religious divisions in the migrant heartlands of Melbourne and Sydney.
The Weekend Australian has been told security officials put the number of Australians suspected to have travelled to the Syrian and northern Lebanon theatres at "more than 100".
Officials suspect they may be participating in the conflict in a variety of roles, including as combatants.
The passage of Australians to Syria is part of a general Islamification of the Syrian opposition movement, which has seen thousands of foreign fighters pour across Syria's northern, southern and eastern borders to participate in the fighting.
Syria's main opposition group is the Free Syrian Army, a secular armed fighting force for the Syrian Opposition Coalition, which has been officially recognised by Australia, France, the US and Britain.
Fighting alongside the FSA, which has sought to distance itself from the extremist groups, are a range of Islamist factions. They include conservative, but mainstream, Salafist groups as well as hardcore jihadists with international links.
One of those groups, Jabhat al-Nusra, was recently listed as a terrorist organisation by the US due to its links with al-Qa'ida in Iraq. US officials credit al-Nusra with more than 600 attacks across Syria, including the summary execution of prisoners.
In a sign of how prominent the Islamists have become in the Syrian opposition, al-Nusra boasts about 7000 fighters and has become one of the most effective military brigades in the fight against the Assad regime.
Aside from the risk of injury or death, Mr Drennan said Australians who travelled to foreign hotspots risked being prosecuted in Australia for terrorism or foreign incursion offences carrying penalties of between seven and 20 years' jail.
Australian officials say the Syrian uprising represents the first time al-Qa'ida has played a frontline fighting role in the Arab Spring, which began in December 2010.
They believe Australians have been drawn to the conflict mainly for two reasons: sectarian loyalty with their fellow Sunnis or the desire to wage jihad. The latter reason is of most concern to counter terrorism officials.
Mindful of the precedent set in Afghanistan during the 1980s, when the struggle against Soviet occupation produced a generation of well-trained, highly radical jihadists who would later wage war against the West, officials worry the Syrian cause could produce a crop of Islamists with combat skills and training.
They stress the problem is not yet on the same scale as the Soviet jihad nor are there indications any of the returned Australians have evinced a desire to attack targets in Australia.
They add that community leaders in Sydney and Melbourne have been quick to recognise the threat to social cohesion that the conflict poses and for the most part have been effective in quelling sectarian tensions.
Most of those known to have travelled to Syria are Lebanese dual nationals who enter Syria via northern Lebanon. However, other dual nationals are suspected to have travelled to the conflict zone.
Although separated by a line on the map, the territory around southern Syria and northern Lebanon forms a single cultural community. Many of Australia's Sunni Lebanese citizens have family in northern Lebanon which, like Syria, has been wracked by periodic outbursts of sectarian fighting since the uprising began 21 months ago.
Two Australians are known to have been killed in Syria, apparently while taking part in the fighting. Sydney sheik Mustapha al-Majzoub was killed in a rocket attack in August. His supporters said he was conducting humanitarian work, but counter-terrorism officials contacted by The Weekend Australian confirmed he was a known extremist. In October, Melbourne kickboxer Roger Abbas was killed, according to his family, after he was caught in crossfire while carrying out humanitarian work.
Abbas had posted on a Facebook tribute page set up to honour al-Majzoub.