New Zealand's foreign minister has confirmed a New Zealand nurse has been held captive by the Islamic State group in Syria for almost six years, information long kept secret for fear her life might be at risk.

The status of nurse and midwife Louisa Akavi, now 62, is unknown but her employer, the International Committee of the Red Cross, says it has received recent eyewitness reports suggesting she might be alive.

The New York Times on Sunday became the first media organization to name Akavi, ending a more than 5 ½-year news blackout imposed by the New Zealand government and Red Cross with the cooperation of international media.

The collapse of ISIS has raised hopes Akavi and two Syrian drivers kidnapped with her might now be discovered.