Australia's official terror threat level could be upgraded in the next few days.
Its domestic spy agency, the Australian Security Intelligence Organisation (ASIO), said the threat has been building during the past year and there was an elevated level of concern.
Since 2003 the threat has been at medium, which means an attack is possible and could occur. Raising it to high would mean an attack is considered likely.
ASIO director-general David Irvine said he was looking at an increased risk from the influence of the conflict in Syria and Iraq and the rise of the Islamic State.
He said he was worried not only about young Australians going there to fight, but also about those returning who might be preparing for attacks inside Australia.