New Zealand's Covid-19 alert level has risen to three and the country will go into a full lockdown at 11.59pm on Wednesday, Prime Minister Jacinda Ardern has confirmed.

Photo: RNZ / Dom Thomas

The time will be required to ensure essential services are in place, and the country will move to level four and will remain at that level for four weeks, Ardern said.

The country now has 102 confirmed Covid-19 cases and the Ministry of Health says the virus is spreading in the community.

Ardern warned the lockdown could be extended for longer if the spread of the virus was not brought under control.

"This will literally save lives, thousands of lives."

She said all of NZ must prepare to go in self-isolation now to "break the chain" of community transmission.

Schools will be closed from tomorrow.

Full details are available on the official government website at covid19.govt.nz/.

Watch the latest media conference here:

The prime minister said non-essential business in NZ must all close, including bars, cafes, restaurants and cinemas.

She said these decisions would place the most significant restrictions on New Zealanders' movements in modern history.

"I do not underestimate what I'm asking New Zealanders to do, I know it's huge."

She confirmed supermarkets, doctors, pharmacies, service stations, and access to essential banking services will be available throughout New Zealand at every alert level.

Ardern said the country must give time for supermarkets to restock their shelves.

"There will be enough for everyone if we shop normally."

Alert level three is where the disease is increasingly difficult to contain. Public venues and non-essential businesses will need to close.

Alert level four is when there is sustained transmission. Everyone would need to be isolated from each other. Essential services will continue, but everyone would be asked to stay at home.

Ardern said there was a small window to get ahead of the spread of the virus, and "we have to act now".

She said people can leave their home for fresh air and for exercise, but it must be solitary and people should only spend time with people they are in self-isolation with.

Public transport will be only available for people working on essential services.

Ardern warned that things will look worse, before they get better, and in the short term, the number of cases will rise because it is in the community.

She said medical modelling without measures showed that tens of thousands of New Zealanders could die of Covid-19.

That worse case scenario was "simply intolerable" and would represent the greatest loss of New Zealanders in our history.

"As a government, we will do everything in our power to protect you.

"Now I'm asking you to do everything you can to protect all of us."

She said the failure of anyone to play their part in the coming days would put the lives of others at risk.

"We are in this together."

Read more about the Covid-19 coronavirus: