Changes have been made to New Zealand's mask-wearing protocol as Omicron cases increase and the country settles into the red setting of the traffic light system. 

Prime Minister Jacinda Ardern announced a number of changes to face mask rules in the red setting of the Covid Protection Framework during a press conference this afternoon. 

The changes affect those visiting food and drink businesses and other close proximity settings, as well as some primary and secondary students and workplaces with vaccine mandates in place. 

The changes come into force in nine days and include: 

- Masks must now be worn at food and drink businesses and close-proximity businesses, events and gatherings. The existing exception of when you are eating or drinking still applies. The changes did not apply to non-public facing workplaces, swimming pools and gatherings where you have the exclusive use of a premises.

"We are, for instance, asking people at restaurants when they enter, when they get up to use the bathroom to use masks," Ardern said. 

- Face coverings now must be an actual mask as opposed to scarves, bandanas or T-shirts pulled up over the face, for example.

"This is to ensure it is a mask that is designed to cover your nose and mouth properly." 

- All workers who are legally mandated to be vaccinated must also wear a medical-grade mask. For example, a Type 2R or Level 2 mask or above while working in public-facing roles. That included the widely available blue medical grade that many were already wearing, Ardern said.

- Primary and secondary school students, Year four and up, were already required to wear a mask. For consistency, these students would now need to wear a mask on Ministry of Education-funded school transport services and public transport.

The new mask protocols would further help the "slow down of Omicron", Ardern said. 

"I know some of these adjustments may cause challenges but the science has been updated and these adjustments will slow the spread of the virus, save lives and give us time to get more of the eligible population boosted." 

The changes would come into force in nine days, allowing them to be gazetted and for workforces, in particular, time to prepare. 

The ministry would also update guidance on masks for the public, Ardern said, including how to safely reuse masks and ensure the best fit. 

"We've looked at a lot of overseas data on who's most successfully managing Omicron. Masks play a significant role when done right. 

"We've made a major shift in New Zealand by adopting their widespread use. Now we just need to tighten them up slightly so we get best out of this really important measure." 

The update on New Zealand's second full day under nationwide red traffic light restrictions, where gatherings of more than 100 people are banned. 

The whole country moved to red at 11.59pm on Sunday after Omicron case numbers increased with nine cases of the variant detected in the Nelson/Marlborough region. 

Today, health officials announced 10 new cases of the variants, as part of the 25 total Covid-19 cases detected in the community. 

As of this afternoon, 29 community cases of virus were associated with the January Omicron cluster - including one new case in the Nelson/Tasman region, one in Palmerston North and two in Tauranga. 

Of today's new cases, at least six were in Auckland and were linked, directly or indirectly, to a family event and other associated events in Tāmaki Makaurau on the weekend of January 15 and 16 where the Omicron cluster began forming.