New Zealand's Prime Minister Jacinda Ardern carries her lunch during an event in Welcome Bay near Tauranga, New Zealand. (AP)

Wellington: New Zealand will lift coronavirus restrictions across the country on September 21, except in its biggest city, Auckland, which is the epicentre of a second wave of infections, Prime Minister Jacinda Ardern said on Monday.

Ardern said Auckland's restrictions would be reviewed next Monday. She also said the government would immediately ease all physical distancing requirements on planes, a boost for Air New Zealand, which has had to limit passengers on its planes for months.

“I know this change will make a real difference to Air New Zealand and those parts of the country seeking increased numbers of visitors,” Ardern said in a news conference in the South Island city of Dunedin, where she is on an election campaign trip.

Masks will still be mandatory on all public transport, she said.

New Zealand, a nation of five million, had appeared to have succeeded in halting community transmission of COVID-19, but a fresh outbreak in Auckland in August prompted the government to place the city back in lockdown.

Prime Minister Jacinda Ardern, who is facing a general election on Oct. 17, scaled back the restrictions this month, but the city is still under alert level 2.5, meaning social gatherings of more than 10 people are not allowed.

Ardern cabinet will review the current rules for Auckland at its meeting on Sept. 21, with a view to increasing gathering limits if the situation stays stable.

That change, if it comes, will take effect on Sept. 23, she said.

New Zealand on Monday reported one new case of coronavirus in the community, taking the total number of cases to 1,447 and 24 deaths.