Nine people have now died in this country from the coronavirus, with six of them residents of the Rosewood Rest Home in Christchurch.
This is the highest number of deaths in a day in New Zealand.
Director-General of Health Ashley Bloomfield said all four deaths were men, and three were linked to the Rosewood cluster. Two of them were aged in their 80s, and one was in his 90s.
The fourth death was a man in his 70s in Wellington, with that death linked to overseas travel. He was admitted to hospital on 22 March and had been "quite unwell for some time".
"It is a sobering reminder of what is at stake here," Dr Bloomfield said.
He offered condolences on behalf of New Zealand.
"Whether husbands, partners, fathers, grandfathers, brothers, uncles, cousins or friends, wherever they fit in their wider whānau, we are thinking of them and of you."
Dr Bloomfield said aged residential care settings were very vulnerable.
"We have had cases to date in six facilities around the country, this is from a total of about 650 facilities nationwide."
He said the fact that relatively few facilities had reported infections was the result of hard work on the behalf of the rest and care homes, alongside the Ministry of Health.
Every new arrival in a facility must now go into isolation for 14 days now, and meals are taken separately.
Other health Ministry work to help aged care facilities was also underway, including work to supply PPE.
There was also a low threshold for testing, Dr Bloomfield said.
Dr Bloomfield said there would be an announcement later in the week about funding for aged care facilities.
"I have also decided to commission a review of the aged residential care facilities where we have had cases ... we think it's a very good point in time to undertake a review," Dr Bloomfield said.
Dr Bloomfield said the review of aged care facilities was "good practice".
Dr Bloomfield said as someone who had lost both his parents, he absolutely understood how people who couldn't be with loved ones when they died would be feeling. That was why the rules around visiting relatives in hospital were being reviewed.