Jacinda Ardern says Victoria, Australia's COVID-19 spike a reminder New Zealand 'not immune' to second wave of coronavirus

A resurgence of COVID-19 in Australia is a sombre reminder of the ongoing threat coronavirus poses to New Zealand, the Prime Minister says.

After seemingly getting its COVID-19 outbreak under control, Australia's daily cases have been building over the last week - and on Monday it recorded 81 new cases, less than three weeks after recording just two earlier in the month.

The majority of these cases are in the southern state of Victoria, which has now entered its second period of lockdown and closed its borders in response to the spike.

Speaking at a press conference on Wednesday afternoon, Jacinda Ardern told media our goal now is "to preserve those freedoms" we enjoy at alert level 1.

And Ardern says while we've recorded two consecutive days with no new coronavirus cases, what's happened in Victoria is a warning to New Zealanders not to get complacent.

"While we have low cases and days with zero, Victoria too was in a position of low cases and days with zero just three weeks ago," she said.

"In the past 24 hours it has had 64 new cases, and today moves to local lockdown across 36 suburbs and has closed its borders. It is an example of how easily the virus can take hold again and why vigilance is so important.

"It's a good reminder that New Zealand is a safe haven in a dangerous world. But we are not immune to what is happening in the rest of the world, and we will all battle this global pandemic for some time to come."

Earlier on Wednesday, the Director-General of Health Ashley Bloomfield said it shows territories with "strong protocols" in place to keep COVID-19 at bay were still at risk.

"The number of COVID-19 cases worldwide continues to increase and some countries continue to experience a resurgence," Bloomfield said.

"Yesterday's developments from Victoria with the imposition of targeted lockdowns reinforce that even countries with strong protocols in place, such as Australia, may need to change tack, sometimes really quickly.

"We have worked very closely with Australia and will continue to do so. We will watch the latest developments closely to see how this approach and the measures they are putting in place, such as localised lockdowns, play out.

"A key takeout for all of us from this is that we must continue to be on guard and vigilant, as individuals, as communities and as a country."

While New Zealand has managed to restrict any new cases to our border, the Government's handling of the coronavirus crisis since eradicating the disease last month has not gone without criticism.

In June, Ardern, Bloomfield and Health Minister Dr David Clark came under intense scrutiny after two sisters were allowed to travel from Auckland to Wellington for a funeral without being tested for COVID-19.

It later emerged that one of the women was exhibiting symptoms on the day they were allowed to leave, and both tested positive for coronavirus.