The Defence Force is battling a blaze in bushland at the Waiouru Military Camp in the central North Island, which started during a live fire exercise yesterday.
It is the second fire to have been sparked during military exercise yesterday, the other on an Army base near Christchurch.
Both are under investigation.
A Defence Force spokesman said the Waiouru blaze had burnt through about 350ha but was now contained in a 5ha gully of dense vegetation in the Three Kings area.
Five civilian helicopters and a Royal New Zealand Air Force helicopter are fighting the blaze, which started during an exercise by the Singaporean Armed Forces.
Extra resources have been deployed to Waiouru, including extra personnel and a water tanker, to assist the Singaporeans in dealing with hotspots in areas burnt by the fire.
The spokesman said there had been no injuries as a result of the fire.