The global struggle against Islamic State and its jihadist offshoots will rage for at least a decade with the greatest risk to Australians posed by a resurgence of extremism in Indonesia, a leading terrorism analyst warns.

Rohan Gunaratna, the head of the Nanyang Technological University’ International Centre for Political Violence and Terrorism Research in Singapore, says the world is now effectively involved in a “second war on terror” with IS a far more formidable foe than al-Qaeda in the post 9/11 era.

“I think any way you look at it we are in for a struggle with IS and its offshoots lasting at least a decade,” Professor Gunaratna said in an interview with The Australian Financial Review.

“You could call it a second war on terror and it will be every bit as challenging if not more challenging for the West as the first,” he said.