Key refused to provide details on those involved, but confirmed there was a small number of New Zealanders involved with anti-government groups in Syria, New Zealand Herald reported on Monday.

He would not say whether some were linked to al-Qaeda groups, but Australia's Federal Police have told media that up to 100 Australians were understood to be fighting in Syria, and about six had been killed "while fighting with al-Qaeda-linked terrorist groups''.

Key said that since 2005, the law had provided for the Minister of Internal Affairs to cancel a passport in some circumstances.

"So we have the capacity to cancel a passport if we believe somebody is going into a war zone, for instance, to fight in a way we don't think is a sensible step for them to take.'' He said it was also possible to cancel a passport on national security grounds after somebody had left the country.

As a result, they would have to stay where they were or be deported to New Zealand. He said fewer than 10 passports had been cancelled since that law passed in 2005, some of which related to Syria.

Australia has also cancelled passports of those involved in the fighting and has warned they will be treated as national security threats upon their return.

Key said the current powers were sufficient to deal with matters when those people returned to New Zealand, and each case would be different. "But there is always a risk that somebody who goes into that environment comes back to New Zealand in a radicalized state.''

"We believe we have enough powers to deal with the situation. Australia's numbers are much greater and they've taken a different perspective on it.''

He said it showed the importance of giving intelligence agencies the powers they had. "From time to time we need to track the activities of New Zealanders, we need to be sure of their whereabouts and we certainly need to be clear that if they return to New Zealand, whether they pose a threat to other New Zealanders if they have become radicalized.''

A recent British defense study showed that about 100,000 militants, fragmented into 1,000 groups, are fighting in Syria against the government and people.

NTJ/SHI