Australian authorities charge five men attempting to reach Syria by boat with terror related offences

Australian authorities are expected to seek the extradition of five men charged with terrorism offences for allegedly planning to travel to Syria via Indonesia and the Philippines in a fishing boat from northern Australia after being arrested last week.

The men, all aged between 21 and 31 face a Cairns magistrates court on Monday, to face extradition to Melbourne for prosecution after charged with making preparations for incursions into foreign countries "for the purpose of engaging in hostile activities" at the weekend.

If convicted, the men, all originally from Melbourne, face a maximum penalty of life imprisonment.

Australian Attorney General George Brandis confirmed to reporters in Brisbane on Sunday that the men's passports were cancelled several months ago as their intentions to travel to the Middle East to engage in "terrorist war fighting" was known, and subsequently put under increased surveillance.

"When it became clear to them that they wouldn't be able to leave the country in an orthodox way, they remained under surveillance so that if they attempted to leave the country in this very unusual way they would be able to be stopped and they were," Brandis said.

The men were arrested after towing a seven-meter fishing boat from Melbourne to Cairns in the tropical north of Queensland state.

Authorities are seeking to prosecute the men in Melbourne as that is where they had bought the fishing boat and allegedly plotted their route, Brandis said.

Though Brandis and Australian authorities stress there are no current or impending threat of possible terror attacks in Australia, the country has been on heightened alert since September 2014 with authorities arresting numerous persons in connection to domestic terror plots.

It's believed approximately 100 people had left Australia for Syria to fight alongside organisations such as Islamic State (IS), and fears are growing battle hardened operators could entice domestic attacks via online communications.

Authorities are becoming increasingly concerned about online "grooming tactics", similar to those used by sexual predators, being used in Australia to radicalise young teenagers.

Late last month, an Australian teenager was arrested and charged with plotting to commit a terror attack on the nation's national day of remembrance for its service men and women, also known as ANZAC day.

The plot was described by a senior politician as "chilling" given the age of the suspect.

In early December 2015, Australian counter-terrorism authorities arrested a 20-year-old man and a 15-year-old teenager in connection with an alleged plot targeting Australian government buildings, including the Australian Federal Police (AFP) headquarters in Sydney.

The two men and three others already in jail on related charges are believed to be associates, of those who radicalized 15-year-old Farhad Jabar who executed police accountant Curtis Cheng in early October 2015. Jabar's sister fled to Syria the day before the attack.

In late February, the teenage bride of an Australian terrorism suspect was arrested by counter-terrorism authorities for allegedly possessing a knife, an Islamic State flag and documents relating to a terror attack. Her husband is already in custody on terror related charges. Endit