Attorney-General George Brandis says at least 20 Australians have been killed in the conflict so far from an estimated total of 90 Australians who have travelled to the region.
'This number has risen in recent weeks, with several Australians understood to have died in fighting against government forces, including in Kobane,' Mr Brandis told The Australian.
He's accused I.S of duping westerners into fighting their war for propaganda purposes.
'Australian youths, and many young men and women from Western countries, are being lured by the falsehood of a noble battle against an oppressive enemy,' he said.
'In reality, they are merely taking part in acts of thoughtless violence, in many cases against innocent civilians, on behalf of ISIL, which is intent on recklessly enslaving, raping and murdering those with a contrary view to their own.'