Five terror suspects who planned to join Islamic State after leaving Australia by boat will continue to be held in custody without charge.

The five men, including Islamic preacher Musa Cerantonio, were arrested in Cape York on Tuesday after allegedly towing a seven-metre boat from Victoria to far north Queensland with plans to travel to Syria to join IS.

The Australian Federal Police (AFP) on Thursday successfully applied in a Cairns court for the men to be held in detention for an extended period under “specified time” provisions of the Crimes Act.

• Men arrested over alleged plan to take boat to join IS
• Prakash’s death “huge blow” to IS

The legislation allows for a period of detention without charge of up to seven days. A spokeswoman said the AFP would not be providing details of the length of time granted.

“These detention provisions recognise that terrorism investigations can be complex and that there may be legitimate reasons for extended periods of detention for suspects in such matters,” the AFP said in a statement.

“The use of specified time provisions during investigations like this is vital to gathering, assessing and compiling relevant evidence.”

The AFP said the presumption of innocence still applied to the group.

It came after Attorney General George Brandis said there was a significant risk the group would have made it to Indonesia and on to Syria.

They were under surveillance prior to their arrest, he added.

Deputy Prime Minister Barnaby Joyce said the men did not appear to be “the brains trust of the operation”, having broken down after towing their boat.

“The vast majority of Australian people, despite their creed, despite their colour, despite where they’re from, are just looking at this bunch of buffoons saying what on earth are you doing,” he said.

“It’s like a Monty Python movie and it’s come to an end.

“Welcome to the constabulary you clowns.”