At least six people have died and others remain unaccounted for following a fire in a hostel, New Zealand's prime minister has told local media.

Emergency services were called to the four-storey Loafers Lodge hostel in Wellington just after midnight local time (12:30 GMT Monday).

Dozens were rescued from the building, but police said a number of people remained unaccounted for.

Chris Hipkins warned the number of dead was likely to increase.

Upon arrival at the blaze, firefighters found the top level of the building ablaze. By 04:00 at least 20 fire trucks were involved in helping extinguish it.

Fire and Emergency District commander Nick Pyatt described the fire as Wellington's "worst nightmare".

Police warned they could not be more specific on the number of deaths until they could access the building.

Mr Pyatt also said the building contained asbestos and urged locals to wear a face mask and keep their windows closed to avoid inhaling the smoke, the New Zealand Herald reported.

"This is a tragic event for all involved. My heartfelt condolences go to the loved ones of those who have lost their lives", he said.

Authorities rescued at least five people from the roof of the burning building and one person sustained serious injuries after jumping from the third floor of the building to escape the flames, local media reported.

Mr Hipkins described the fire as "tragic" to TVNZ and paid tribute to local firefighters "who have put themselves in harm's way over past hours to get people out of the building and put the fire out", the NZ Herald reported.

"It's an absolute tragedy and you know, Wellington is a small close-knit community", he said to New Zealand's AM show.

The cause of the blaze is currently unknown, but local media reported that police were investigating whether it was deliberately lit. (BBC)

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