People started heading to supermarkets on Sunday evening despite the Prime Minister's calls for Kiwis not to rush to shops during her announcement of alert level changes across the country.
Traffic also built on some motorway stretches ahead of Auckland's move to Covid-19 alert level 3 from 11.59pm for three days.
The rest of New Zealand is at level 2, Ardern announced. Those alert levels will be reviewed in 24 hours.
Supermarkets and petrol stations would remain open so there was "no need to rush out to get any essential items," Ardern said.
Despite the calls, queues formed at some Auckland supermarkets last night.
In Freeman's Bay, Jacqueline Campbell had a trolley full of groceries at New World on a day she'd normally not do any shopping.
Campbell said she and her husband had anticipated there'd be a jump in alert levels.
"My husband came in and said: 'We should probably get some food'."
She said when the family heard the Prime Minister would address the country, lockdown seemed the likely outcome.
Campbell, originally from the US, said she did not want the pandemic to grow out of control as it had in her homeland. "I'm glad that they're doing everything they can to get it under control."
Under level 3, travel in and out of the city is also heavily restricted - a possible explanation for heavier than normal traffic heading south on Auckland's Southern Motorway on Sunday night.
A Waka Kotahi NZTA camera at the Southern Motorway at Greenlane at that time showed busy southbound traffic but empty northbound lanes.
The transport agency said at 9.30pm that journeys from Te Atatu to Manukau which, in free-flowing conditions, would take 22 minutes were instead taking 37 minutes.
The move to level 3 comes after three new Covid-19 cases in the community were reported earlier on Sunday - a mother, father and daughter from Papatoetoe.
Ardern said the change in alert levels was the "right thing to do".
Ardern said the Government was asking Aucklanders to "stay home" and people should work from home where possible.
That means children are being asked to stay home from school.
Public venues, such as pools and playgrounds, will be closed.
"You'll remember that supermarkets, pharmacies, primary produce retailers and petrol stations, they will all remain open throughout so no need to after this announcement to rush out to get any essential items. All of those providers ... they will all be open and continue to be open," Ardern said.
"If you know someone in Auckland, reach out and please check on them. And if you're in Auckland please check on your neighbours, ensure they are looked after and supported," she said.
"I'm asking New Zealanders to continue to be strong and to be kind."
She said we all have this feeling of "not again".
She reassured the nation: "We are going to be okay."
Less than one hour after the lockdown announcement, queues were building at the Countdown Ponsonby supermarket.
One customer remarked: "It must be another rush for the toilet paper."
Countdown in Howick was particularly busy for a Sunday night following the news of the move to Level 3 lockdown.
One shopper said the store wasn't packed, but some items were popular. Flour and chocolate needed to be restocked.
One customer said they decided to shop on Sunday just in case there was a shortage of items they'd usually get on their Monday grocery shopping.
Workers looked busy ready to restock items that were running low.
More people appeared to be wearing masks than usual.
On Ponsonby Rd, Revelry bar manager Darren Taylor understood level 3 meant the bar would have to close.
"So for us it's not a good thing. We need to be at level 2."
Taylor was with a friend about to have dinner when the lockdown announcement was made.
The hospitality industry has been hard-hit in previous lockdowns.
Taylor hoped the alert level would be lowered by the weekend.
In the meantime, he said friends in the industry were philosophically describing the latest lockdown as a "three-day vacation".
LEVEL 3: Auckland
- Stay at home and work remotely if possible
- Schools and daycare only open to children of essential workers
- Gatherings restricted to 10 people - and for funerals, tangi and weddings only
- Travel restrictions with borders around Auckland
- Public venues such as pools and playgrounds closed
LEVEL 2: Rest of New Zealand
- People can still go to work
- Schools and daycare remain open
- Gatherings restricted to 100 people
- Travel into Auckland restricted