Auckland will move to Covid-19 alert level 3 from 11.59 tonight for three days.
The rest of New Zealand will be at level 2 over the same time period, according to Prime Minister Jacinda Ardern who made the announcement tonight.
At the same time, Auckland will undergo a testing blitz to find out how extensive the outbreak is.
Speaking to reporters tonight, Ardern said the lockdown was the "right thing to do.".
The three community cases announced earlier today triggered the new alert level restrictions.
At 8.25pm, a nationwide push alert went out to mobile phones across the country, warning of the upcoming lockdown.
"Customers travelling from Alert Level 2 regions are able to transit through Auckland on their way to other Alert Level 2 regions. »