One New Zealander is believed dead, and Key says with a small group of Kiwis combating in Syria, there may have been other casualties as more body bags are expected.

With the death toll so high and impossible to track in the foreign-hatched insurgency war in Syria, even the United Nations has given up counting.

A Syrian government official told the United Nations "of the terrorists killed in Syria some came [from] New Zealand."

"We've lost contact with him and as I understand it his family have lost contact with him," says Key.

A Syrian group said it knows of only one New Zealander in Syria, Weiming Chen, a Chinese-born artist believed to be fighting with the terrorists.

But Key won't say if he's the man killed or even if he was an insurgent.

"Maybe he's part of the Red Cross there, who knows? Maybe he was part of some other humanitarian organization. Maybe he was a doctor providing humanitarian medical services," says Key.

Amira Ali, 22, may have been the first New Zealander to die in Syria. She is thought to have been killed in Aleppo in January. Her mother was a New Zealand citizen.

Amira had told her family she was going to Syria for humanitarian work.

A total of one New Zealander has been killed, two Auckland brothers had their passports stripped before intending to go to Syria war and another Kiwi was arrested in Australia before leaving.

Besides Ali and Chen, there is a total of six either combating, or trying to battle in Syria.

Key says it's a handful and that includes those who have tried and failed to get there. But even though it's a small group, he says more New Zealand casualties are possible.

NTJ/MB