Prime Minister Jacinda Ardern announces New Zealand border closure to non-residents

All of New Zealand's borders will close to non-residents  in an attempt to stop the spread of COVID-19.

Only New Zealand citizens or permanent residents and their families will be able to enter the country from 11:59pm on Thursday.

Prime Minister Jacinda Ardern announced the decision on Thursday evening, saying it follows a number of tourists refusing to isolate.

"I've been increasingly concerned visitors to New Zealand are not adequately self-isolating or refusing not to and that is an unacceptable risk that we must end," she told media.

The law also extends to the Pacific Islands.

People from the Pacific were exempt from the previous rule of mandatory self-isolation for 14 days upon entering New Zealand.

Some exceptions to the rule will remain in place, said Ardern.

"A small number of exemptions will remain around the Pacific Islands, especially those who must travel here for humanitarian reasons,"

Key health professionals will also be exempt.

New Zealand has reported 18 cases of COVID-19 in the past 48 hours, and the first cases have been reported in Fiji and Samoa.

All confirmed cases in New Zealand have been from overseas travel.

Ardern acknowledged  the travel ban will cause further harm to the economy but said a country "decimated" by the virus would be in more danger. 

Australia has introduced the same rule, which will come into effect from 9pm on Friday night.

Prime Minister Scott Morrison told media the move was due to 80 percent of the country's 638 cases had come in from overseas.

'For Australians, of course, they will be able to return and they will be subject, as they already are, to 14 days of isolation upon arrival back in Australia. "