New Zealand has announced it was shutting down its largest city, Auckland, after four new cases of Covid-19 were discovered in the city, the first evidence of domestic transmission after being coronavirus-free for 102 days.
Director General of Health Ashley Bloomfield said the four confirmed cases were within one family in South Auckland.
They had no history of international travel and family members have been tested and contact tracing is under way.
News of the cases sent panic across the country with media reporting people rushing to supermarkets to stack up, and businesses preparing to shut.
Prime Minister Jacinda Ardern said Auckland would move to level 3 restriction from tomorrow as a "precautionary approach", which would mean people should stay away from work and school, and gatherings or more than ten people would again be restricted.
The restriction would be applied for three days until Friday, which she said would be enough time to assess the situation, gather information and make sure there was widespread contact tracing.
"This is something we have prepared for," Ms Ardern said in a surprise news conference, adding that the increased caution was becasue the source of the virus was unknown.
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"We have had a 102 days and it was easy to feel New Zealand was out of the woods. No country has gone as far as we did without having a resurgence. And because we were the only ones, we had to plan. And we have planned," she said.
There is one new case of #COVID19 to report in managed isolation in New Zealand today.— Ministry of Health - Manatū Hauora (@minhealthnz) August 11, 2020
It has been 102 days since the last case of COVID-19 was acquired locally from an unknown source. Read more at https://t.co/wJiwvObGNA pic.twitter.com/enOlzulLAT
New Zealand is set to vote in a national election on 19 September.
Ms Ardern said she has not given any consideration to the impact of the new restrictions on the polls at this stage.
Travel into Auckland, on the North Island, would be restricted unless you live there, she said.
Auckland Mayor Phil Goff said in a statement: "I am urging Aucklanders to come together like we did last time to stamp out community transmission. Please remain calm, please do not panic buy and please follow the lockdown rules."
Ms Ardern also said the rest of New Zealand was entering alert level 2 from tomorrow for three days. This would mean social distancing measures would be applied again and mass gatherings would be limited to 100 people.
For Auckland:— Unite against COVID-19 (@covid19nz) August 11, 2020
Under Alert Level 3, you are encouraged work from home if you can.
If you are currently in Auckland and do not live in Auckland, we suggest that you go home. Practice good hygiene and be conscious of your health. We recommend that you keep your bubble small.
New Zealand marked 100 days without a domestic transmission of the coronavirus on Sunday, but warned against complacency as countries like Vietnam and Australia which once had the virus under control now battle a resurgence in infections.
New Zealand was placed under a tight lockdown for weeks after reported its first known case on 26 February and the last case of community transmission was detected on 1 May.
Ms Ardern had declared the virus had been eliminated from the community.
Mr Bloomfield said the unknown nature of the new cases mean it was likely there would be more positive case in the coming days.
He said people should use masks in places where it was hard to physically distance.
"The case is a wake up call for any complacency that may have set in," he said.
An infectious disease expert in New Zealand said he was hopeful the shutdown will be effective.
Speaking on RTÉ's Today with Sarah McInerney, Dr David Murdoch said New Zealand's response to Covid-19 has been to react early and react hard and said people have been very "spooked" by the outbreak in the Australian state of Victoria.
He said a mandatory two week quarantine remains for anyone arriving in New Zealand.