The governments Covid-19 website says that all of New Zealand will move to the red traffic light setting from midnight tonight.

The announcement was confirmed by prime minister Jacinda Ardern at an unscheduled press conference at 11.10am this morning (January 23).

It comes after five flights were on Saturday linked to nine Covid-19 cases reported in the Nelson Tasman region on Friday.

An Air New Zealand crew member on the same Auckland-Nelson flight as the nine cases - who are all part of one household - tested positive for Covid-19 on Saturday.

The prime minister said these cases have now been confirmed as the Omicron variant.

"These cases are in a single family that flew to Auckland on 13 January to attend a wedding and other events on the weekend of January 15 and 16," the PM said.

"An initial estimate suggests that there were well over 100 people at these events.

"This cluster has already led to an additional infection of a fully vaccinated Air New Zealand flight attendent who picked it up on a flight 5083 on January 16, from Auckland to Nelson, that the family was on.

That flight attendant has worked for additional flights whilst infectious. We were also informed late yesterday of a further case who was at the wedding."

The prime minister said a link between the index case and the border has not yet been established which means Omicron is now circulating in Auckland and possibly in the Nelson Marlborough region.

"Our strategy is to slow the spread of Omicron down, this includes boosters and public health measures such as mask wearing and restrictions on gatherings, while keeping the pressure off our health system to protect those most at risk of getting sick," the PM said.

Traffic Light Setting Red

PHOTO: Supplied