From midnight Sunday, everyone arriving in New Zealand will have to isolate themselves for 14 days, Prime Minister Jacinda Ardern has announced.

The tighter border controls were announced during an update by the prime minister on New Zealand's response to the Covid-19 outbreak on Saturday afternoon. She said while it is not realistic for New Zealand to only have a handful of coronavirus cases, the changes would slow the spread of infection.

"New Zealand has today, relative to other countries, a small number of cases," Ardern said.

"We must plan and prepare for more cases. We must go hard and we must go early. We must do everything we can to protect the health of New Zealanders."

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The restrictions apply to New Zealand citizens and residents as well as international visitors.

People travelling from the Pacific Islands to New Zealand will be exempt, unless they show symptoms of coronavirus.

The new measures mean New Zealand will have the strongest border restrictions in the world, apart from Israel and some Pacific Islands, which have effectively closed their borders.

As of midnight Saturday, no cruise ships will be able to dock in New Zealand until June 30.

Strict new border exit rules to the Pacific Islands will also be put in place.

ALDEN WILLIAMS/STUFF Prime Minister Jacinda Ardern has announced strict new rules around self-isolation for arrivals to NZ.

Anyone with coronavirus symptoms will not be allowed to travel there and those who have been to other overseas countries will have to wait 14 days before going to the Pacific Islands.

Close or casual contacts of confirmed cases of Covid-19 will also be barred from travelling to the Pacific Islands. All travellers' temperatures will be taken before they leave for the Pacific Islands.

Travel restrictions would be reviewed in 16 days, the prime minister said.

Ardern urged New Zealanders not to travel overseas unless it was absolutely necessary.

We have significant capacity for testing, Ardern said. "It is there and available." There are enough resources for 550 people to be tested per day.

Medical practitioners would use their clinical judgement when deciding who needed to be tested, the prime minister said.

STACY SQUIRES/STUFF The National Remembrance Event for the March 15 terror attack has been cancelled due to coronavirus.

Ardern reiterated public health messages to prevent the spread of infection. "Wash your hands," she repeated three times.

People should also stay home and avoid contact with older people if they're sick and stop greeting each other with a handshake or hongi.

Finance minister Grant Robertson will announce an economic response on Tuesday.

The Government will announce guidelines on large mass events next week too.

In the meantime, people planning on hosting such gatherings should contact their local public health authority, Ardern said.

Soon after the press conference Air New Zealand said it was reviewing the impact of the "new measures announced this afternoon on its operations and will adjust its capacity accordingly. We expect to provide an update on network changes over the next few days".

It comes after a sixth case of the novel coronavirus was confirmed in Auckland.

A man in his 60s who had recently returned from the United States tested positive for the illness on Friday night.

RICKY WILSON/STUFF Prime Minister Jacinda Ardern at Saturday's press conference regarding Covid-19 Coronavirus.

The National Remembrance event for the March 15 terror attack has also been cancelled due to the outbreak, as has a memorial service which was due to be held in Auckland.

On Friday, Auckland's Pasifika Festival and several other events was called off over concerns about the virus.

Currently, New Zealand's border is closed to international visitors who have travelled to China or Iran.

People arriving from Italy and South Korea, which have become coronavirus hot spots, must go into quarantine for 14 days.

US President Donald Trump has suspended travel from Europe to try to slow the spread.

Australia has introduced a travel ban on Italy for everyone except Australian citizens or permanent residents.

A New Zealand couple holidaying in Italy who were supposed to be transitting through Australia have been left in the lurch by the ban as they were barred from boarding their flight.

On Thursday, Jacinda Ardern said New Zealand was poised to toughen its restrictions.

The country is in the "stamp it out" or containment phase of our pandemic plan.

Prime Minister Jacinda Ardern on Saturday afternoon announced a range of travel restrictions to slow the spread of Covid-19, with six confirmed cases in the country.

SO WHAT ARE THE NEW RULES FOR NZ?

* Every person entering New Zealand from anywhere in the world will be required to self-isolate for 14 days, excluding the Pacific. These restrictions will all be reviewed in 16 days' time.

* The existing travel ban for China and Iran will continue

* Cruise ships banned from coming to New Zealand, until at least June 30, 2020

* Strict new health measures at the border for people departing to the Pacific

* Measures to help those in self-isolation to be announced next week

* Government will work closely with the aviation sector to encourage airlines to remain active in New Zealand, limiting the impacts on the tourism sector and exporters

* There will be a directive on mass gatherings announced early next week

The prime minister's announcement followed a Cabinet meeting in Auckland on Saturday.