Prime Minister Jacinda Ardern has said officials were looking at tailored criteria for events that may need to be cancelled, such as whether people would be in close proximity to one another.

Prime Minister Jacinda Ardern says gatherings of 500 or more people should be cancelled because of fears of coronavirus.

This covered indoor and outdoor events, but not schools or universities, who would get more specific advice from the Ministry of Education.

More guidelines from ministers will follow for smaller events, such as weddings, and smaller venues such as gyms, movie theatres or places of worship.

Within the next month, about 107 events around the country were expecting more than 1000 attendees, she said. "Our job as a Government is to limit the potential spread of the virus to ensure the health of New Zealanders."

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These would not be the only requirements on gatherings. Ardern said social distancing would be "the new normal" and people who hosted events such as weddings would also see detailed guidelines later in the week about how to host smaller events safely.

Cancelling the events would slow the spread of Covid-19, reducing the number of people infected and to protect those who are more vulnerable to severe illness, she said.

The new rules applied to "non-essential" events such as festivals, fairs, sporting, religious and cultural events. There was no time limit on the advice from the Government.

While it currently excluded schools and universities, the Ministry of Education would be working with those institutions to reduce gatherings with 500 students, as they were able to, she said.

Ardern acknowledged the restrictions could have a huge impact on the arts and culture industry but said it was necessary to keep people safe.

Auckland Writers Festival and Central District Field Days were immediately cancelled in response to the news.

On Sunday, Ardern indicated New Zealand would likely follow Taiwan in advising cancellation of crowded gatherings, which she said had been quite successful.

Meanwhile, Australian prime minister Scott Morrison has advised against all non-essential mass gatherings of more than 500 people, while the Centers for Disease Control and Prevention in the United States has recommended no gatherings of 50 or more people for the next eight weeks

On Monday, organisers of Wellington's annual Homegrown music festival postponed it indefinitely. It was due to be held on Saturday.

Ardern announced on Saturday everyone arriving in New Zealand would have to self isolate for 14 days.

Repeating several times during a press conference in Auckland that it was time to "go hard, and go early," Ardern signalled there would be additional announcements on mass gatherings.

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