Prime Minister Jacinda Ardern said the death reinforced the importance of the move to Alert Level Four, and the measures being are taken to limit the spread, break the chain of transmission and prevent deaths.

The first death from coronavirus in New Zealand has been confirmed, as the total number of people with the virus climbs to 514.

Director-General of Health Dr Ashley Bloomfield on Sunday said a West Coast woman in her 70s died of the virus on Sunday morning.

The woman had initially been diagnosed with influenza that was complicated by an underlying health condition, but a positive Covid-19 test came through on Saturday. The 21 staff who treated her were self-isolating. The woman was admitted to Grey Base Hospital, Greymouth, on Wednesday.

Prime Minister Jacinda Ardern, speaking alongside Bloomfield at the Beehive, said: "Today's death is a reminder of the fight that we have on our hands".

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Bloomfield said health officials had counted 63 new cases of Covid-19 on Sunday, of which three were probable cases.

ANDY JACKSON/STUFF Taranaki people continue to be tested at the Phoenix Urgent Doctors in the Richmond centre in New Plymouth.

The total now stood at 514 cases, including 56 who had recovered. There were nine people in hospital; three in Wellington, and a case each in Blenheim, Nelson, Whangarei, Taranaki, Waikato and Dunedin.

There was one person in an intensive care unit, on a ventilator. On Saturday there were two Covid-19 patients in ICU, one being the West Coast woman who has since died.

The majority of cases remained linked to overseas travel, Bloomfield said, though community transmission and clusters of the virus have been identified. He was unsure how many cases were confirmed or probable cases of community transmission.

MONIQUE FORD / STUFF Director-General of Health Dr Ashley Bloomfield said the first Covid-19 death was a woman in her seventies who had initially been admitted with what was thought to be influenza complicated by a underlying chronic health condition.

The fatal West Coast case had a connection to overseas travel but health officials were yet to establish whether this was source of the virus.

Bloomfield said the woman and her health condition was known to hospital staff, and because she was at first not considered to be a possible Covid-19 case. He was unsure of when the woman was admitted to hospital.

Staff therefore did not wear full personal protective equipment (PPE) as a precaution, as might have been expected, he said. The full gear was worn after the positive test.

None of the staff that had treated the woman were symptomatic, he said, and the hospital had no staffing issues as a result of their self-isolation.

Laboratories were working to process and report test results as quickly as possible, he said.

Taken over a seven-day period, the average daily test number was 1786.

Ardern said it would be an enormously difficult time for the family of the person who died, and she asked that their privacy be respected.

The number of confirmed coronavirus cases have slowed in recent days, from 85 to 83 on Saturday, and then 63 cases on Sunday. But New Zealand could not be complacent, Ardern said.

"Even with the measures we now have in place, we will continue to see more people get sick, because of the time it takes to get unwell," she said.

KEVIN STENT/STUFF The All of Government Covid-19 national response team, from left, Dr Peter Crabtree, Controller John Ombler, Dr Ashley Bloomfield, Sarah Stuart-Black and Mike Bush, Commissioner of Police.

The coronavirus Cabinet committee met on Sunday morning to discuss the ongoing border restrictions and quarantine measures in place.

Ardern said on Saturday, 840 Kiwis returned to New Zealand and some 300 were expected to cross the border on Sunday.

This was a dramatic fall in the number of returning Kiwis, she said.

"I know [the quarantine of returnees] is causing concern for their families, and I do acknowledge that concern. We have to keep in mind though that returning New Zealanders through no fault of their own do carry the greatest risk."

Ardern said she had seen reports of comments online that "that I would say amount to bullying".

The 514 people who have or had the virus were having a difficult time already, she said, and needed support not abuse.

Police Commissioner Mike Bush had also informed Ardern that more than 1000 callers have dialled the 111 emergency to alert police to people breaking the lockdown.

"Many Kiwis that I know are keen to ensure that collectively the rules are being followed."

She said police now had an online form on the 105.govt.nz website to report such possible breaches, which would reduce the load on 111 and help police triage the complaints.

In the hour after Ardern spoke, police issued a statement saying the website was already straining with number of people trying to access the form.

*This article has been updated. Ministry of Health director-general of health Dr Ashley Bloomfield had said the woman tested positive on Friday. Her test results were confirmed on Saturday.