Omicron cases have almost doubled overnight, to 810 community cases today, from 454 yesterday - with more than 600 in Auckland alone.
"The sharp increase in new cases today is another reminder that, as expected, the highly transmissible Omicron variant is now spreading in our communities as we have seen in other countries," the Ministry of Health says.
"Our expectation is that cases will continue to increase over the coming weeks and we’re asking people to do all they can to slow the spread of the virus and protect themselves and their whānau."
The ministry says the most important step anyone can take to prepare for Omicron is to book their vaccine.
"Every dose counts and lowers the chances of getting very sick and being hospitalised."
Thirty-three people are in hospital, five more than yesterday. None are in intensive care.
Tāmaki Makaurau accounts for more than 75 per cent of the cases, with 623 new cases in the community. Waikato has the next largest number, with 81.
There are also 13 new cases in Northland, 11 each in Bay of Plenty and Lakes, eight in Hawke’s Bay, three in MidCentral, six in Whanganui, five in Taranaki, and three in Tairāwhiti.
Wellington has 15 new community cases, Hutt Valley 10 and there are two each in Nelson Marlborough and South Canterbury. In Canterbury there are three new cases and the Southern DHB region has 14.
Eighteen new cases have been identified at the border.
The number of active cases is now 4,072.