A national state of emergency has been declared in New Zealand amid evacuations, power cuts and fears of fatalities from the havoc wreaked by ex-cyclone Gabrielle.

Emergency Management Minister Kieran McAnulty made a declaration early on Tuesday (local time) as Kiwis woke to flooding, power loss, road closures and phone network outages from the massive storm.

Thousands of people have been evacuated across the country and fears are held for the lives of several New Zealanders.

In Muriwai, a coastal town west of Auckland, a volunteer firefighter is missing feared dead, and another is in a critical condition after a home collapsed under a landslide.

The navy was also searching for two boats in waters north of Auckland, although one had been found by later on Tuesday morning.

News outlet Stuff also reported people were trapped in cars along State Highway 5 between Napier and Taupo, where communications are patchy.

Prime Minister Chris Hipkins said there had been extensive damage across the country.

“I want to acknowledge the situation that New Zealanders have been waking up to this morning – a lot of families displaced, a lot of homes without power, extensive damage done across the country. It will take us a wee while to get a handle on exactly what’s happened,” he said in a national update on Tuesday.

“People will be aware a national state of emergency has been declared, and that means that we’ll be throwing everything at this to make sure we’re providing as much support to the response as possible. We have the Defence Force on the ground now, already providing a lot of logistical support.”

Mr Hipkins had been stranded in Auckland overnight after Air New Zealand grounded all of its domestic flights. He hoped to get to Wellington later on Tuesday for full briefings with authorities.

Earlier, Mr McAnulty said the extreme weather was having “major impacts across much of the North Island”.

“This is a significant disaster with a real threat to the lives of New Zealanders,” he said.

It is only the third time a national emergency declaration has been issued, after the 2011 Christchurch earthquakes and the COVID-19 pandemic.

“We are through the worst of the storm itself but we know we are facing extensive flooding, slips, damaged roads and infrastructure,” Mr McAnulty said.

Overnight, Gabrielle continued its southwards march before parking near Great Barrier Island, to the north of the Coromandel Peninsula.

It is expected to move eastwards, and by 10am Tuesday (NZ time) it was in the Bay of Plenty, north of Tauranga.

Its massive size is whipping up destructive winds all across North Island.

More than 100,000 Kiwis have lost power in the past 24 hours. They include the entire city of Napier, on the east coast of the North Island, which lost power on Tuesday morning.

Residents of multiple Napier suburbs were told to “evacuate immediately” early on Tuesday and “go immediately to your nearest hill” as flooding in Hawke’s Bay continued to worsen.

Emergency crews were rushing to help people reportedly stranded on roofs across the region.

But there are also questions about how residents can get to safety,  ith roads cut off and bridges closed across the region. Some residents have issued urgent pleas through social media for news of loved ones they have not been able to make contact with.

Across the North Island, regional states of emergency have been declared in at least areas, including Auckland, Northland, Thames-Coromandel, and at 4.30am on Tuesday, Napier and Hastings.

MetService executive Lisa Murray said some areas of the Coromandel, the region closest to the storm’s eye, had already had 300 millimetres of rain.

“It really is widespread across the North Island,” she told Radio NZ.

Asked what area gave her the most concern, Ms Murray replied, “There are so many areas … there’s a lot of places in trouble.”

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On the East Coast, the Gisborne and Hawke’s Bay regions have been battered by similar totals, with rivers breaking their banks and forcing evacuations.

“I’ve been in the region over 20 years and this is by far the biggest [storm] … people have not seen a storm like this. It’s a very, very significant event,” Hawke’s Bay civil defence spokesman Ian Maxwell told Radio NZ.

In Muriwai, grave fears are held for the safety of the volunteer firefighter missing after the home’s collapse.

Fire and Emergency NZ chief executive Kerry Gregory said the property was too unsafe to search.

“Our thoughts are with our firefighters, and with their loved ones. We are also providing support to the other members of their brigade,” he told TVNZ.

Transport authority Waka Kotahi reported about 50 road closures, including the main north-south highway in several places and key arterial roads in the Coromandel and East Coast.

Cyclone Gabrielle will continue to wreak destruction across North Island on Tuesday.

Red wind warnings remain for Auckland, Northland, the Coromandel and Taranaki, with gusts of up to 140km/h forecast.

Red rain warnings have been extended in Northland, the Coromandel and Hawke’s Bay.

A majority of the North Island, including Wellington and Napier, are under orange warnings for wind, suggesting up to 120km/h gusts, as is the northern region of South Island.

-with AAP