New Zealand's health chief says he is "disappointed" by a man with COVID-19 who travelled into the country from Australia while he was still awaiting coronavirus test results.

Key points: New Zealand now has eight confirmed cases of COVID-19

New Zealand now has eight confirmed cases of COVID-19 Two of those are foreign travellers

Two of those are foreign travellers The latest cases follow Prime Minister Jacinda Ardern's announcement that anyone arriving into New Zealand after midnight Sunday must self-isolate for 14 days

New Zealand's Ministry of Health said, as of Sunday afternoon, there were eight confirmed cases of COVID-19 in the country — up from six on Saturday — after two foreign travellers tested positive.

One of the new cases, a man in his 60s, arrived into Wellington from Brisbane on Air New Zealand flight NZ828 at 12:05am (local time) on Saturday.

Both the man and New Zealand health officials were informed that morning by his Australian doctor of his positive test result.

New Zealand Director General of Health Ashley Bloomfield said the man had symptoms when he was tested, but was asymptomatic when he arrived in New Zealand.

Dr Bloomfield said the man's case, alongside that of another woman from Denmark who also tested positive, was evidence that stricter border controls announced yesterday were justified.

"I'm surprised the person took the flight in the first place, I'm pretty disappointed actually," Dr Bloomfield said.

"At best this action has inconvenienced a number of people and at worst it may have put people at risk.

"It was an inappropriate thing to do."

Dr Bloomfield said the man, now symptom-free, was now self-isolating inside a Wellington hotel room with his partner and another family member

He did not require hospital care.

Dr Bloomfield said his health officials were in contact with their Australian counterparts about what advice the man received before departing.

New Zealand strengthens borders

The latest New Zealand cases followed Prime Minister Jacinda Ardern's announcement yesterday that anyone arriving into New Zealand after midnight tonight (10:00pm AEDT) would be forced to self-isolate for 14 days.

It was among some of the strictest border control measures introduced by a country in response to the coronavirus pandemic, which has killed more than 5,800 people worldwide.

New Zealand PM Jacinda Ardern said anyone arriving into New Zealand after midnight tonight would be forced to self-isolate for 14 days. ( ABC News: Kevin Nguyen )

Australian airlines were scrambling to get passengers into the country before the deadline.

Virgin Australia has re-timed two of its flights landing in Dunedin and Auckland from Brisbane and Melbourne, respectively, to arrive before the midnight deadline.

However, it is understood flight VA99 scheduled to land in Christchurch at 11:55pm from Melbourne could not be adjusted without cancelling other services.

New Zealand Customs told the ABC that passengers on any plane which was "on blocks" — meaning it was parked at a gate with wedges under its wheels — before 1:00am local time would not be subject to quarantine measures.

Passengers walking out of the international arrival gate at Christchurch Airport expressed mixed feelings about the restrictions.

Some of them learnt about it mid-air.

"On the flight … the pilot announced it. I was like wow, that was right under the gun," said Siddiqi Ray from Los Angeles.

She said she flew to New Zealand to escape the "mayhem" and the "total panic" cause by coronavirus in the United States.

"There's no food on the shelves in the grocery store, there's no toilet paper anywhere," she said.

She hoped to stay in New Zealand until the "craziness is over".

Sue Kerr, from Perth, originally planned to land on Monday to visit family but said she "booked another flight at great expense to come beat the embargo".

Meanwhile John Bates and Nadia Reece, from Broome in Western Australia, said they only learnt about the self-isolation order two hours before departing.

"We were lucky we got in just in time," Mr Bates said.

"But we were thinking we're not sure if we'll get out on the day we needed to.

"Apart from that, we're very happy that New Zealand is doing the measures that they're taking."