New Zealand's Delta COVID-19 outbreak grows to 72 cases

New Zealanders are being told to prepare for an extension to the week-long lockdown as COVID-19 outbreak expanded by another 21 cases.

COVID-19 testing health workers at the Pages Rd Marae. Source: AAP

New Zealand has recorded 21 new COVID-19 cases for the second day in a row, swelling the outbreak to 72.

The outbreak, New Zealand's first time dealing with the Delta variant, remains centred on Auckland with 20 of the new cases reported in the country's biggest city.

The New Zealand government has ordered a week-long nationwide lockdown to curb the spread of the virus, due to last until Tuesday.

COVID-19 Minister Chris Hipkins pre-empted an announcement due on Monday around the future of lockdown restrictions, warning Aucklanders they should prepare for a longer stay at home.

While New Zealand's lacklustre vaccination rates has allowed for the outbreak to take hold, Mr Hipkins reported a rollout milestone.

As of Saturday, one million Kiwis are fully vaccinated - just less than 20 per cent of the population.