Foreign fighters have been flooding Syria since the beginning of the bloody Civil War. With estimates of up to 11,000 foreigners in Syria, Western powers are increasingly worried about the potential national security threat posed by returning fighters.

One of the more concerned countries is Australia, where suburbs have been disrupted by numerous beatings, assaults, shootings, and property damage.

Melborne and Sydney, the most populous Australian cities, have become the centers of violence between groups who are for and against the Syrian government of President Bashar al-Assad.

More than 15 incidents have been reported in the suburbs of the country involving members of the Lebanese, Turkish and Syrian communities and this has the Australian government concerned about its own national security.

"In Australia, like many other countries, we are witnessing a growing trend of citizens traveling offshore to engage in, or support terrorist activities or conflict," said Attorney General George Brandis. "These individuals not only potentially breach Australian laws and commit offences offshore, but upon their return to Australia they pose a significant national security risk."

There are no exact evidence on the number of Australians who have gone to fight in Syria, but estimates suggest the number is about 200. Australia's large Lebanese community with ties to the region has enabled volunteers' movements in and around Syria.

The death of a young Australian man who was killed with his wife in Syria last week has prompted a stronger rhetoric from the Australian government. The man was recruited to fight against the Assad regime and had alleged ties to Al Qaeda and Jabh at al Nusra.

The government has also stepped up prosecutions and the Australian domestic spy agency, ASIO, has confiscated the passports of anyone suspected of traveling to engage in "politically motivated violence."

Norwegian terrorism expert, Thomas Hegghammer, released a report last February showing that one in nine Westerners who fight in foreign extremist insurgencies ends up becoming involved in terrorist plots back home.

The Australian government is concerned that the experience, new skills, ideologies, and networks formed on Syria's battlefield could see the fighters posing a threat to Australia upon return.

Reach Executive Producer Syuzanna Petrosyan here. Follow her on Twitter.