The government has announced a ban on indoor gatherings of more than 100 people to help stop the spread of Covid-19.

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It follows the prime minister's announcement on Monday that indoor and outdoor gatherings of 500 people or more should be cancelled.

The measures are being put in place, despite there being no evidence of a community outbreak in New Zealand.

Health Minister David Clark said he understands this will be "deeply disappointing" for many people.

"Especially those who have large celebrations planned in coming weeks. While it is unfortunate, we have to put these measures in place. Reducing close contact is an essential part of our plan to protect the health of all New Zealanders and we ask everyone to do the right thing and to comply.

"Large gatherings and events are a high risk environment for the spread of infectious diseases like Covid-19, because people often behave in ways that facilitate transmission at these events.

"People share food or drinks, sit or stand very close together for long periods of time and may cough or breathe on each other," he said.

Clark said the government is working with the hospitality sector to develop guidance over the next 24 to 36 hours about the implications for them.

"I think it's fair to say that things in pubs, clubs and restaurants will not be the same as they are today. We need to work with the industry to make sure we have the right solution in place to ensure social distancing and to ensure [they] have measures in place that will enable the tracing of any people who are there," he said.

Clark said it was not possible at this stage to say how long these measures will be in place, but warned we could be in this situation for some time yet and the advice is "if in doubt, cancel".

"I really want to acknowledge that this will affect people's lives. Weddings, funerals and other social gatherings are significant events in people's lives.

"I can understand the upsetting nature of that for people who have events planned but we need to take a precautionary approach," he said.

Clark said Medical Officers of Health have the power to ensure the measures are enforced, and he implored people to comply with this and other public health measures.

"Anyone who has thumbed their noses at this critical public health advice, you are putting the health of your family, your friends, and your country at risk.

"It is up to all of us to play our part to unite against Covid-19, it needs the whole community to play ball and enforce these rules sensibly," he said.

People who ignore these measures could face up to six months in prison, or a fine of up to $4000.

Clark said regardless of size, if people are feeling unwell or they should be in self-isolation, they should not attend any events.

Bridges welcomes ban

National leader Simon Bridges described the ban as a "positive step forward" but said the government needs to go further and close our borders to non-New Zealand citizens and permanent residents.

"The number of Covid-19 cases are increasing rapidly. We've seen enough internationally and in New Zealand to know that this is the right move.

"All 28 diagnosed cases in New Zealand have come from people travelling from overseas.

"The EU has closed its borders but it was too late to stop widespread community outbreak. We can't make the same mistake. We are a small isolated nation and we should take advantage of our geographical position," Bridges said.

The Ministry of Health has produced guidance around these new measures and it will shortly be available on the website covid19.govt.nz.

Last week, the government said any gatherings of 500+ people would not go ahead, and that still applies for any outdoor events.

Today, Director-General of Health Dr Ashley Bloomfield confirmed there were eight new cases of Covid-19 in New Zealand, bringing the total number to 28.

If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs)

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