Deadly New Zealand flood crisis spreads

Another person remained missing, police said on Sunday.

The focus of the emergency has since moved south, with Waitomo District - about 220 kilometres from Auckland - declaring a state of emergency late on Saturday.

The nation's weather forecaster, MetService, warned of more severe weather on Sunday and Monday for the north island, including in Auckland where severe thunderstorms were possible.

Intense rainfall could also cause surface and flash flooding, MetService said.

Police said they were assisting with traffic management and road closures in Waitomo District on Sunday after heavy rainfall "caused numerous slips, flooding and damage to roads".

In nearby Bay of Plenty there was also "widespread flooding", police said, as well as a landslide that had knocked down a house and was threatening neighbouring properties.

"Police are asking those in areas experiencing severe weather to ... not attempt to travel on the roads, many of which are currently undriveable," police said.

Flights have resumed at Auckland Airport, which had closed domestic and international operations on Friday.

Air New Zealand said its international flights in and out of Auckland would resume from noon on Sunday (2300 GMT on Saturday).

On Saturday, Prime Minister Chris Hipkins, who took office less than a week ago, flew by helicopter over Auckland before touring flood-hit homes. 

He described the flood impact in the city as "unprecedented" in recent memory.

There were more than 2000 calls for assistance and 70 evacuations around Auckland - the nation's largest city - due to the inundation, the New Zealand Herald reported on Saturday.

On Friday, social media showed firefighters, police and defence force staff rescuing people from flooded homes using ropes and rescue boats.

City rainfall records were broken in the weather event, caused by warm air descending from the tropics.

Auckland Airport logged 249mm in the 24 hours to 9am Saturday, beating the 1985 high of 161.8mm.