Australian police have charged five men suspected of planning to travel to Syria to join the Islamic State.

"The primary focus of the investigation is - has been to - prevent the crime of foreign incursion. That is the crime that is committed when people travel from Australia to participate in a civil war or terrorist war fighting overseas, as it will be alleged these five men were preparing to do," said George Brandis, Austalian attorney general.

The men were charged with preparing to enter a foreign country "for the purpose of engaging in hostile activities". The offence carries a maximum penalty of life imprisonment.

Officials said the suspects' intention to travel to the Middle East to fight with the Islamic State were known to the authorities, and that their passports had earlier been cancelled. The five will appear in court on Monday.