New Zealand will be in lockdown for at least another four days.

Prime Minister Jacinda Ardern has just announced that Alert Level 4 will continue nationwide until 11.59pm on Tuesday, August 24.

Cabinet will meet on Monday to make a decision whether it needs to be extended beyond then.

Ardern said: "As you can see from the update, we are in a reasonable position.

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"But I need to stress that it is early days and there is a lot we don't know."

At this stage there were no random cases popping up, she said, so the Ministry were beginning to identify the edges of the outbreak.

But, she said, with Delta it is too soon to draw any conclusions, especially as the locations of interest included bars, schools and churches, known to increase the spread.

Hundreds who had been at locations of interest were now isolating across the country, including South Island.

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"We are still waiting on a large number of contacts to be tested," she said.

"We just don't quite know the full scale of this Delta outbreak. All in all this tells us we need to continue to be cautious."

Therefore the lockdown extension was necessary, bringing the total to seven days.

Ardern said it is likely Auckland, the centre of the outbreak, will need to be locked down longer, and possibly Coromandel.

"It's difficult for us to say how long at this stage. That's why we'll come back in, report in on Monday, for the whole country, including Auckland."

There are 11 new cases of Covid-19 in the community today, bringing the total to 31.

Three of the cases are in Wellington, with the remainder in Auckland. The Wellington cases had recently travelled to Auckland and visited a location of interest there.

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Director-General of Health Dr Ashley Bloomfield said there are 162 close contacts identified throughout rest of New Zealand, as of 2pm today.

"As expected . . . people who have been in locations of interest in Auckland have dispersed right throughout the country."

Some 642 close contacts have been identified in the Auckland and Waikato regions.

More follows.