New Zealand's prime minister Jacinda Ardern postponed the country's general election on Monday by a month to October 17 as the city of Auckland remains in lockdown due to a growing coronavirus outbreak.

Ardern bowed to pressure to delay the polls after parties complained they could not campaign with nearly a third of New Zealand's five million people under lockdown in Auckland.

"Ultimately, the October 17 ... provides sufficient time for parties to plan around the range of circumstances we will be campaigning under,"  Ardern said at a news conference.

The prime minister ruled out delaying the polls any further, as her Labour Party maintains a strong lead over the conservative National Party in opinion polls.

With more than 21.5 million cases worldwide, a second wave of infections is also threatening further disruption in many countries. The disease has killed more than 766,000 people globally, and the number of deaths hit 50,000 in India on Monday, which is still battling its first wave with 2.5 million infections -- the third-highest in the world.

New Zealand on Monday recorded nine new cases of COVID-19, taking the number of active cases to 78. There have now been a total of 1,280 cases in the country, and 22 deaths.

An earlier election would have worked in Ardern's favor, as her success in stifling COVID-19 and keeping the country virus-free for 102 days until the latest outbreak had boosted her popularity.

The election was scheduled for September 19 and New Zealand law requires it to be held by November 21. Advance voting will now start on October 3.

The Election Commission said it was ready to hold a vote with health measures including hand sanitiser and physical distancing in voting centres, protective gear for staff and contact-tracing systems.

Almost a week after the discovery of New Zealand's first locally transmitted coronavirus outbreak in more than three months, its origin remains a mystery.

The Pacific island nation had benefited from its remoteness early in the pandemic, when Ardern swiftly closed off the international border and imposed one of the world's toughest lockdowns. Those measures stamped out local transmission for some 100 days.

Genome testing of the latest batch of infections has confirmed it is a new strain, officials have said, probably from Australia or Britain.

With the clock ticking to get the latest outbreak under control, that has raised the tricky question of how it entered a country that has been largely closed off for months.

(With input from Reuters)