Prime Minister Jacinda Ardern gives an explanation of any move to level 3, but stops short of announcing a move out of level 4.

Kiwis will be asked to stay at home and keep to a slightly larger "bubble" of family members if New Zealand leaves level 4 lockdown.

Prime Minister Jacinda Ardern provided a much-anticipated explanation of life under Covid-19 alert level 3 on Thursday afternoon, saying most people will need to remain at home. Bars and cafes will remain closed.

"Just like when you're recovering from an illness, you still primarily stay home ... Many things will feel the same as they do now," she said.

New Zealand spent two days in level 3 before entering a level 4 lockdown; whether the country will re-enter the now stricter alert level 3 in a week's time remains uncertain.

ALDEN WILLIAMS/STUFF An empty Cashel St in Christchurch. Life under level three is uncertain, and streets may remain fairly quiet. (file photo)

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Ardern and her Cabinet will decide on Monday whether New Zealand will leave lockdown at midnight the following Wednesday, April 22, or whether the most restrictive measure will be extended.

At a press conference last week, Ardern said the updated detail on the Covid-19 alert system should not be taken as an indication that New Zealand would leave lockdown next week.

If the country enters alert level 3 people will be permitted to expand their contacts to include close family members, a caregiver, children in shared care, or a defacto partner.

Construction and forestry businesses will be able to resume work, as will other businesses that can maintain physical distancing requirements. Workers will be asked to work from home where possible.

Cafes and bars, which deal with customers face-to-face, will not open. If businesses can deal with customers in a "contactless" way, they will be permitted to open, including retail, hardware and restaurants.

Early childhood centres and schools will partially reopen, for children up to the age of Year 10 only. Attendance will be voluntary, meaning families who want to keep their children at home can.

ROSA WOODS/STUFF Prime Minister Jacinda Ardern will provide detail on what life under level 3 will look like on Thursday afternoon. (file photo)

People will be able to travel within a region as needed, and further movement between regions will be restricted.

Low-risk activities will be permitted as long as they are non-motorised, meaning there will be no boating but swimmers and surfers can again take to the ocean.

"You can fish from the shore. However ... Now is not the time to take up a new activity that you have never done before. It is too risky," Ardern said.

Funerals, tangihanga and weddings attended by no more than ten people will be deemed acceptable, but food or receptions cannot take place.

"The principle here is that it is ideal that you still keep your contact with a range of other people very, very limited," Ardern said.

"Keeping in mind that many people are now going to be exposed to people in a workplace ... if you are going back to your private life and extending your exposure that causes an exponential increase to the people you're exposed to.

"With level three, it's very gradual, it's a progressive system, and we really want to keep it as limited as possible."

Also further detailed was alert level 2, which would: allow gatherings of 100 people indoors or 500 people outdoors; sport and recreation activities; public venues such as libraries, most businesses and schools to open; and discourage non-essential travel between regions.

Ardern said New Zealand had acted early to prevent a "wave of devastation" and the country would never know what would have happened without such a lockdown.

"We should not confuse the success of our actions with overreaction."

At the Thursday press conference, director-general of health Dr Ashley Bloomfield said there were 15 new cases of Covid-19 in New Zealand. Another 42 people had recovered from the virus, adding to a total of 770 recoveries.

There were no further deaths from the virus.

Alert Level 3

- Stay home other than for essential personal movement – including to go to work, school or for local recreation.

- Physical distancing of two metres outside home (including on public transport), or one metre in controlled environments like schools and workplaces.

- Immediate household bubble can expand to reconnect with close whānau, bring in caregivers or support isolated people.

- Schools (years 1 to 10) and early childhood education centres can safely open, but will have limited capacity. Children should learn at home if possible.

- People must work from home unless that is not possible.

- Businesses can open premises, but cannot physically interact with customers.

- Low risk local recreation activities are allowed.

- Public venues are closed (e.g. libraries, museums, cinemas, food courts, gyms, pools, playgrounds, markets).

- Gatherings of up to 10 people are allowed but only for wedding services, funerals and tangihanga.

- Healthcare services use virtual, non-contact consultations where possible.

- Inter-regional travel is highly limited (e.g. for essential workers, with limited exemptions for others).

- People at high risk of severe illness (older people and those with existing medical conditions) are encouraged to stay at home where possible, and take additional precautions when leaving home. They may choose to work.