New and worrying cases have emerged in New Zealand’s Delta outbreak, prompting Jacinda Ardern’s government to extend the national lockdown.

The whole of New Zealand will stay under the country’s highest restrictions until at least Tuesday night, with another cabinet meeting on Monday to decide on further moves.

The outbreak grew by 11 cases to 31 on Friday, with three cases in Wellington – the first evidence of spread outside Auckland.

Ms Ardern said New Zealand was “in a reasonable position” in its first meeting with the dreaded Delta variant, but it was “too soon to draw any conclusions”.

“It is early days and there is still a lot we don’t know,” she said.

“We’re dealing with a large number of locations which we sadly know from experience do lead to more cases.”

The country’s director-general of health, Ashley Bloomfield, recommended a longer lockdown for Auckland – until August 31 – but Ms Ardern said she would make that call on Monday.

“We believe we’ll be in a better position to make an assessment about all of NZ with that full seven days,” Ms Ardern said.

While COVID-19 has spread to Wellington, many on the South Island – which has not had a community case of COVID-19 for over a year – feel they should be unburdened.

Associate Health Minister Ayesha Verrall said the government needed to see not just absence of the virus across New Zealand but proof of its absence through strong testing rates.

Health authorities and COVID-19 modellers expect there are many further cases in the community, awaiting detection through testing.

On Friday morning Dr Verrall, an infectious diseases physician drafted into government by Ms Ardern, confirmed a new case visited two Auckland hospitals.

The young man is at Waitakere Hospital but spent time at North Shore Hospital, possibly while infectious.

“Action is taken at both hospitals to ensure the safety of the staff and patients there,” Dr Verrall said.

About 30 hospital staff had direct contact with the man, and have been stood down to be tested.

Three Auckland schools have had staff or students test positive to the virus, and NZ Post has also confirmed an employee at an eastern Auckland operations centre tested positive.

So far, all cases to have been genomically sequenced have shown a link to the believed origin of the outbreak: A returned Kiwi who travelled from Sydney on August 7.

“On the good news … we are starting to build a picture of the edges of this cluster,” Ms Ardern said.

“We don’t have random cases popping up outside of those places we expect them.”

-AAP