The Prime Minister says the Government made it clear it did not want a New Zealand nurse captured by ISIS named.

Earlier the International Red Cross said it made the decision to identify Louisa Akavi in full alignment with the Government.

However, Jacinda Ardern told Mike Yardley the Government was aware of the agency's plans but didn't agree with them.

"We were aware of the plans but we made consistently known our view that it would be our preference that our collective position of it not being in the public domain remain the case."

"We were aware of their plans but did not see that as an endorsement."

Ardern said despite the disagreement, the Government has worked collaboratively with the Red Cross for a number of years and this shouldn't undermine that relationship.

However, when asked whether the Government is doing everything it can to rescue Louisa, Ardern said she will not be commenting on the case further.

At least two people have described seeing the nurse in December, at a clinic, in one of the final villages held by Islamic State.

It's believed she may now be in a camp in Northern Syria.

Emma Beals is a Journalist specialising in aid work in Syria and told Tim Dower after five and a half years as a hostage she may be afraid to come forward.

"There have been sightings of her throughout her captivity that have been verified to differing degrees. The common understanding is that she is alive, she certainly was believed to be alive in December."

"She has been a hostage for five and a half years, it's a very long period of time to build up fear in a person. We don't know what they may have said to her, she may be very frightened of them," she said.

The camp Louisa is believed to be in is made up of 70,000 people, most of whom are ISIS families. Beals said that may be contributing to her not coming forward.

"She may be very fearful of them, they have treated her very poorly to date. So I don't think we can make any judgements about why she may or may not have made herself known if she is in that camp."

She said it's hard to know whether naming her was the right call.

"There's no right answer in these cases. It's something that those that are close to Louisa, her family, her employer, the Government, need to make in consultation with each other and do what they think is best for her."

Beals said pressure from international media has been mounting, which made it incredibly difficult for the Red Cross to keep her identity a secret.

"That position has been held very firmly for five and a half years, and became increasingly difficult and I think there was a decision taken to use that pressure to try and find some information that might help to bring her home."