A fire at a multi-story hostel in Wellington, New Zealand, has left at least six people dead and officials warned the number could rise.

Up to 30 others were believed unaccounted for after the blaze broke out overnight at a four-storey hostel building in downtown Wellington, capital of New Zealand, police said on Tuesday.

Fire and Emergency were called to the Loafers Lodge hostel on Adelaide Road in central Wellington around 12:30 am Tuesday, where a fire started from the top floor.

A total of 52 people were taken out of the building and at least five were rescued from the roof, but others remained unaccounted for, according to the police.

Five people were sent to hospital, including two in a serious condition.

A spokesperson from the fire and emergency department said there were around 90 people living in the building, and after evacuation, around 30 people were still unaccounted for.

Talking to a morning news program, New Zealand Prime Minister Chris Hipkins said there could be more fatalities.