A "significant number" of Australians have taken up "leadership roles" in the barbaric Islamic State terrorist group, says Foreign Minister Julie Bishop.

And Ms Bishop says authorities know about 100 more people in Australia who are supporting up to 60 Australians who are fighting alongside terrorists in Syria and Iraq.

Minister for Foreign Affairs Julie Bishop. Credit:Getty Images

Ms Bishop has issued a "call to other nations" to build a "coalition of support" involving "Arab nations" to counter home grown terrorist activity.