(Adds Ardern comments, details on queues at supermarkets)
* Auckland stay-at-home order, restrictions on gatherings
* Long queues outside Auckland supermarkets
* Australia's Melbourne in day 2 of 5-day lockdown
* Melbourne's UK variant cluster now 16 cases
By Praveen Menon
WELLINGTON, Feb 14 (Reuters) - New Zealand's Prime Minister Jacinda Ardern on Sunday announced a three-day lockdown in the country's biggest city Auckland, after three COVID-19 cases emerged, the first local infections since late January.
Level 3 restrictions will require everyone to stay home except for essential shopping and essential work, Ardern said, repeating the strict approach the country has taken over the past year in virtually eliminating the pandemic.
"We have stamped out the virus before and we will do it again," Ardern told a news conference in the capital, Wellington.
New Zealand, which had gone more than two months without local infections before the January case, is to start inoculating its 5 million people against the new coronavirus on Feb. 20, receiving the Pfizer-BioNTech vaccine earlier than anticipated. were raised to level 3 through Wednesday, shutting public venues and prohibiting gatherings outside homes, except for weddings and funerals of up to 10 people. Schools will stay open for children of essential workers but others were asked to stay home.
Sunday's cases were a couple and their daughter in Auckland, the first local infections since Jan. 24.
Health authorities are trying to find out whether these cases involve any of the new, highly infectious variants and how the family contracted the virus, Ardern said.
"Three days should give us enough time to gather further information, undertake large-scale testing and establish if there has been wider community transmission," she said. "That is what we believe the cautious approach requires and its the right thing to do."
The prime minister said there was no need to stock up on goods, as essential services - including supermarkets, pharmacies and petrol stations - would remain open. Still, long queues formed outside Auckland supermarkets, and pictures on social media showed empty grocery shelves.
Airlines have been contacted, as the woman in the infected family works for an airline catering company, LSG Sky Chefs, where she mostly works in laundry facilities, officials said.
The COVID-19 alert for the rest of the country was raised to level 2, with all gatherings limited to 100 people, including at restaurants and cafes.
Australia on Sunday reported two new local COVID-19 cases in the country's second-most populous state, Victoria, on the second day of a snap lockdown to contain the spread of the highly infectious UK variant.
The two cases, including a 3-year-old child, were the first who were not household contacts of a cluster of infected workers at a quarantine hotel at Melbourne airport which triggered the five-day lockdown, health authorities said.
The hotel cluster has now affected 16 people.
New Zealand and Australia closed their international borders and introduced strict social distancing rules early in the pandemic, dramatically reducing the spread of the virus. New Zealand was ranked the best-performing nation in an index of almost 100 countries based on containment of the coronavirus.