New Zealand will require all internationally arriving people - including returning Kiwis - to self-isolate for a fortnight as the country locks down to ward off the spread of coronavirus.

Prime Minister Jacinda Ardern announced the measure on Saturday after an emergency meeting of cabinet.

"We do not take these decisions lightly," she said.

"New Zealand will have the widest-ranging and toughest border restrictions of anyone in the world."

Ms Ardern said the measure applied to people, and not goods, though gave an exemption to people arriving from the Pacific - a region largely devoid of the virus.

The decisions will take effect as of midnight NZDT on Sunday.

New Zealand has just six cases of the disease to date, and none that have been transmitted through the community.

Ms Ardern also announced cruise ships would not be allowed to dock in New Zealand until June.

The decision will be reviewed in 16 days.

Earlier on Saturday, the government announced the cancellation of a national remembrance service in honour of the Christchurch mosque attacks, which took place on March 15 last year.