"Tonight, New Zealand has shown the Labour Party its greatest support in at least 50 years," Ardern said in a powerful victory speech on Saturday night where she referred to the difficult times ahead for New Zealand.

Labour's main opposition, the center-right National Party, is on 27% -- down on last election's 44% and likely to be the party's worst result since 2002.

National leader Judith Collins said she called Ardern to concede defeat and congratulate Ardern on an "outstanding result" for the Labour Party.

The country was one of the first to close its borders, and Ardern announced a nationwide lockdown in March when it only had 102 cases.

New Zealand has reported less than 2,000 total cases and 25 deaths since the pandemic began.

At the start of the year, polls suggested National and Labour could be in for a tight election.

National will reemerge from this loss a stronger, more disciplined and more connected party.

"I say to everybody: we will be back."

Record early turn out

As of Friday, just shy of 2 million people -- or 57% of all enrolled voters -- had already cast their ballot in advance at polling booths around the country, including Collins and Ardern.

Lara Greaves, a New Zealand politics lecturer at the University of Auckland, said the high level of advance voting may have been related to Covid-19 -- voters wanted to avoid lines and the possibility that a fresh Covid-19 outbreak could impact their ability to vote on the day.

She said the turnout could also have been given a boost by two referendums running alongside the election -- one on legalizing euthanasia, and another on legalizing the recreational use of cannabis.