Australia's foreign minister says 150 Australians are fighting with radical militants in Syria and Iraq, raising government fears of a terrorist threat to Australia if the fighters return home.

Foreign Minister Julie Bishop told Australian Broadcasting Corp. on Thursday she has cancelled a number of passports on the advice of security agencies in a bid to reduce the security threat to Australia. She did not say whether the passports were canceled to prevent Australians leaving or returning.

She says Australia will give 5 million Australian dollars ($4.7 million) to the Unites Nations to provide food, medical assistance, tents, access to clean water and hygiene kits to hundreds of thousands pf people fleeing violence in north and northwest Iraq.