An extremist preacher is reported to have been among those arrested over the alleged plans
Five Australians, including an extremist Islamic preacher, have been arrested on suspicion of trying to leave the country on a small boat to join Islamic State fighters in Syria.
The men, aged between 21 and 33, are believed to have previously had their passports cancelled over concerns they intended to join extremist groups abroad.
According to ABC News, Musa Cerantonio, an influential preacher who made calls on social media for Australians to fight in Syria, was among those arrested.
Cerantonio was arrested in the Philippines in 2014 for posts made on Twitter and deported back to Australia, where his passport was cancelled, but no charges were brought.
Police say the group were detained on Tuesday after driving almost 3,000km from Melbourne to Cape York in northern Queensland, towing a seven-metre-long boat.
Victoria Police Deputy Commissioner Shane Patton said police will consider charges after the men were questioned.
"We're investigating the allegation they were planning to make their way through Indonesia to the Philippines, with a view to ending up in Syria," he said.
"We have a requirement to ensure that people can't get offshore to go and fight in other countries, can't get offshore to become hardened terrorists and come back here and pose a risk.
"If disruption means ultimately we don't get sufficient evidence so we can charge them, we'll accept that risk."
Police said they had been investigating the men "for weeks" and there was no domestic terrorism threat arising from the investigation, but warrants have been executed in Victoria and Queensland to gather evidence.
ABC News also claims the group included Shayden Thorne, who was previously sentenced to four-and-a-half years in prison in Saudi Arabia for possessing "terrorism-related material" on a laptop.
He was granted clemency and returned to Australia in 2014, according to the broadcaster.
Australia has been criticised for its tough immigration policies aimed at stopping asylum seekers taking boats from Indonesia to Australia, but few have attempted the journey in the opposite direction.
Some 100 people have left Australia for Syria to fight alongside groups such as Islamic State, Australia's Immigration Minister said last month.