A state of emergency has been declared in New Zealand after 50 more coronavirus cases were confirmed today.

This takes the country's total number to 205.

This afternoon a state of emergency was declared, handing emergency powers to authorities to enforce the nationwide lockdown from midnight tonight.

Director-General of Health Ashley Bloomfield told reporters that six people are in hospital in a stable condition, one in Rotorua, one in Waikato and three in Wellington. Three patients were discharged from hospitals yesterday.

There were 1400 tests processed yesterday, bringing the total number of tests so far to 9780.

He said the cases are being actively being followed up. The majority still had a direct link to overseas travel, or were linked to close contacts of confirmed cases.

Bloomfield said eight people who flew in to Auckland Airport yesterday had tested positive, and Prime Minister Jacinda Ardern has said she was looking at quarantining people arriving into the country.

There were now five community cases related to Auckland's Marist College.

Staff and students from that college should not have contact with other people, Bloomfield said, and they should also keep their distance from people in their own households.

"We do have some community transmission in New Zealand."

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Four were confirmed and number of other cases were being treated a potentially community transmission. There were four community transmission cases, as well as two clusters of cases with links to Marist College and a conference in Queenstown.

Bloomfield expected the number of cases to continue rising for the next 10 days, and the numbers would drop if people stayed at home.

He said there were two possible strains of Covid-19.

"Whatever the strain, we know the way to beat it is the same."

Concerns have been raised by hospital staff about not having masks to wear, but Bloomfield said not all workers would need to wear masks as the risk of catching the virus varied case to case.

He said GPs had moved to doing remote consultations - by phone or video.

Getting personal protection equipment (PPE) to home-care workers was "not something that's usually done", and the DHBs were arranging that gear for staff, as well as workers in supermarkets and other relevant outlets.

Bloomfield said people were being tested for the past couple of weeks even if they did not have a link to overseas travel.

Funeral directors were looking at guidelines to allow very few people to attend a funeral during the lockdown.

State of emergency declared today

Sarah Stuart-Black, director of Civil Defence Emergency Management, said a state of national emergency would be declared in Parliament today.

At 12.21pm, that state was declared by the Minister for Civil Defence Peeni Henare.

This provided access to special powers to combat Covid-19, including powers of requisition and closing roads, and stopping people from doing certain activities.

Stuart-Black said these powers sat alongside other powers to ensure essential services could stay up and running.

"Each of you has a role in helping to save a life," she said.

A mobile alert will be sent between 6pm and 7pm tonight to advise New Zealanders about the state of emergency.

Stuart-Black would be empowered by the state of emergency powers, but she said it would be great if she didn't have to use them.

The legislation allowed the state of emergency to remain in place for seven days, but this can be extended.

"We're really hoping people have heard the messages and understand how horrendous this could get."

Stuart-Black said there would also be no tolerance for people who do not self-isolate.

"We have emergency services available now, the police would have the powers necessary."

Police would give a statement about the escalation that will occur, but the message in the first instances was helping people understand the importance of staying home unless they had a reason to be out in public.

Stuart-Black said a number of issues still needed to be worked through when asked about people in emergency shelters, and homeless people.

Agencies could be used to enforce self-isolation - and if police needed additional support from the military, that was possible.

"I'm hoping it's not going to be necessary."

She said the move to alert level 4 was significant and people needed to take heed of that advice.

"This will be adding a huge amount of anxiety ... you've still got a TV and access to the water from the tap."

Emergency powers could be used but most New Zealanders will stay at home, and in recent emergencies including fires and earthquakes and the mosque shootings, Kiwis had done the right thing to keep themselves safe, Stuart-Black said.

Bloomfield said people should act responsibly. If people went hunting and needed to be rescued, they would take health workers away from the Covid-19 frontlines.

Concern employees not receiving wage subsidies

Ministry of Business, Innovation and Employment deputy chief executive Paul Stocks said employers should pass the Government's wage subsidy scheme on to workers - and if there were cases where that was not happening, MBIE and the Ministry of Social Development would like to know.

The Council of Trade Unions has expressed concern about cases where employers were not passing on the wage subsidy, or forcing workers to take sick leave during the lockdown.

Stocks said that should not be happening.

He noted that public servants had an important role during the lockdown, but they were working from home where at all possible.

Some instances of non-food home delivery services could take place during the lockdown. A fridge, for example, might be needed, but items such as books would not be approved.

Lockdown begins tonight

New Zealand will move to alert level 4 at midnight tonight and will be in nationwide lockdown for at least four weeks - a move Prime Minister Jacinda Ardern says is necessary to prevent up to tens of thousands of unnecessary deaths.

Yesterday the number of confirmed and probable cases rose to 155, including 12 who had recovered and six who were in hospital but have not needed ICU treatment.

The number of new cases was again the biggest daily increase since March 16.

Community transmission cases doubled from two to four, including one in Orewa, two in Auckland, and one in the Wairarapa.

Stocks provided an update last night about what qualified as an essential service, including dairies and self-service laundry services under strict conditions to limit close contact.

The Warehouse will have to close, as well as liquor stores unless they are in a licensing trust areas, where there is nowhere else to buy alcohol.

Yesterday Kiwis overseas were also told to settle where they were as the number of flights home continued to dry up.

Ardern said getting home now would be "very difficult", and overseas travellers in New Zealand who faced a similar dilemma should also prepare for the four-week lockdown.

She added that Kiwis offshore coming home would face more stringent quarantine, but she was still working out where they could be placed without turning a place of quarantine into a petri dish.