Auckland and large parts of the country’s north island remain under a state of emergency, with thousands of properties still without power and hundreds with no water supply.
Auckland emergency management controller Rachel Kelleher said: “We know that there is potential for more adverse weather tonight.”
Deputy prime minister of New Zealand Carmel Sepuloni said: “The most horrific part of it is that we’ve lost lives.”
Police said they found one man’s body in a flooded culvert and another in a submerged car park.
They said fire and emergency crews found a third body after a landslide brought down a house in Remuera. a suburb of Auckland.
Chris Hipkins, who has been prime minister for less than a week after Jacinda Ardern resigned, flew to Auckland by military plane before boarding a helicopter to survey the damage.
“Our priority is to ensure that Aucklanders are safe, that they’re housed and that they have access to the essential services that they need,” Mr Hipkins, who visited flood-hit homes, said.
He added: “This is an unprecedented event in recent memory.”
Air New Zealand has now resumed both international and domestic flights in and out of Auckland after the airport was forced to temporarily close last week.
Another person who was initially reported missing after being swept away by floodwaters has since been confirmed dead.