An Air New Zealand passenger jet taxis at Sydney's airport. File/Reuters

New Zealand announced on Sunday tighter border restrictions as the country's Delta variant outbreak spread beyond the largest city of Auckland, prompting Prime Minister Jacinda Ardern on Sunday to put additional regions into a snap lockdown.

There were 32 new coronavirus cases on Sunday in Auckland, which has been in lockdown since mid-August, and two cases in the Waikato region, some 147 kilometres (91 miles) south of Auckland. Ardern said parts of the region will go into a five-day lockdown.

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She added that the government will decide on Monday whether Auckland's 1.7 million residents will remain sealed off from the rest of New Zealand.

"We are introducing the requirement for air travellers aged 17 and over, who are not New Zealand citizens, to be fully vaccinated to enter New Zealand," COVID-19 response minister Chris Hipkins said.

The normally bustling High Street in Auckland’s CBD is largely deserted during a lockdown. File/Reuters

The national flag carrier Air New Zealand also announced it was introducing a "no jab, no fly" policy for passengers on all international flights from February 1.

While New Zealand was among just a handful of countries to bring COVID-19 cases down to zero last year and largely stayed virus-free until the latest outbreak in August, difficulties in quashing the Delta variant have put Ardern's elimination strategy in question.

The city of two million has been in lockdown for nearly seven weeks as officials grapple with an outbreak of the highly transmissible Delta variant that has so far infected 1,320 people.

About 2,000 people attended an anti-lockdown rally in Auckland over the weekend, with Jacinda Ardern describing the demonstration as "a complete slap in the face" for people who had been abiding by the strict rules banning public gatherings.

"It was illegal and also it was morally wrong," the prime minister said.

New Zealand is pursuing a "Covid zero" elimination strategy.

It had been free of community transmission for six months before the latest Auckland outbreak.