Australia arrests two men for allegedly travelling, or attempting to travel to Syria

Australia on Thursday arrested two men for allegedly travelling, or attempting to travel to conflict zones in Syria and Iraq as authorities become increasingly concerned about the return of foreign fighters with the looming defeat of Islamic State.

Australia, a staunch ally in the U.S. led fight against terror in Syria and Iraq, has remained on heightened alert for home-grown terror attacks for over two years, arresting or jailing at least 45 suspects in connection to domestic terror plots.

The expected return of foreign fighters should Mosul fall and lead to the eventual defeat of Islamic state however is adding another dimension to Australia's security environment. It is believed there are 110 Australians fighting for Islamic state, while 60 have been killed.

"If people have travelled to either Syria, Iraq or some other hostile place where there are hostile activities underway... they would potentially become more radicalised, more extreme and have greater capability (with the use of weapons and explosives) to potentially do some attack," New South Wales Police Assistant Commissioner of specialist operations Catherine Burn told reporters in Sydney on Thursday.

"That is our concern, and our concern is then if they return to our country, they might then use that capability onshore here."

Following a protracted and "very difficult" investigation spanning many years, authorities arrested two men in Sydney on Thursday as part of ongoing inquiries into the activities of people attempting to travel or, or return from the conflict zones in Syria and Iraq.

"We moved as quickly as we (could) in relation to these matters due to the risk these people pose, but also in relation to the ideology they posses," Australia Federal Police (AFP) national manager of counter-terrorism, Assistant Commissioner Neil Gaughan told reporters.

It is alleged 25-year-old Mehmet Biber travelled to Syria in July 2013 to join Jabhat al-Nursa, an affiliate of al-Qaeda in the Arabian Peninsula that is linked to Islamic State, before returning to Australia in February 2014.

A 17-year-old associate of Biber had also attempted to travel to Syria to fight for Islamic State in January 2015, but was stopped at Australia's border. Authorities alleged the 17-year-old male had also played an active role in encouraging another Australian youth to travel to the region.

Though the investigation took over two years, the law enforcement environment had changed quite significantly with various techniques being used, including information gleaned through the court process or other related investigations to bring the matter before the courts, Burn said.

Gaughan would not comment if the two men had been under active surveillance during the investigative period.

Authorities only became aware Biber had left Australia shortly after he had departed in 2013 amongst "significant numbers of Australians travelling offshore (during that time) to take part in the conflict", Gaughan said.

The man was one of seven people recruited by convicted Islamic extremist recruiter Hamdi Al Quidsi. Al Qudsi was sentenced to six years jail for helping a number of men travel to Syria and fight with terror groups.

The Australian government forbids any Australian traveling to war zones without special permission, and those who do and join either side of the conflict face harsh penalties.

Investigations are also ongoing into Australians who have fought for forces battling Islamic State such as the Syrian-Kurdish militant group YPG.

Under controversial foreign fighter laws, any duel national will have their Australian citizenship revoked if they are alleged to be a member of an organization listed on Australia's official terror group watch list. Single nationality Australians face a potential imprisonment of 20 years. Endit