In an unusual move to curb the spread of Covid-19 in New Zealand, Prime Minister Jacinda Ardern has directed a three-day strict lockdown from Wednesday after the island country's largest city Auckland registered the first single case of the virus in six months.

Moreover, the coastal cities of Auckland and Coromandel, where the infected person had resided will be under a seven-day lockdown.

Imposing its toughest level 4 lockdown rules, schools, offices and all businesses will be shut down and only essential services will be operational.

"The best thing we can do to get out of this as quickly as we can is to go hard," Ardern told in a news conference.

"We have made the decision on the basis that it is better to start high and go down levels rather than to go low, not contain the virus and see it move quickly," she said.

Ardern said authorities were assuming "the new case was a Delta variant infection although this has not been confirmed.

The last reported community case of COVID-19 in New Zealand was in February. The country has reported about 2,500 confirmed cases of coronavirus and 26 related deaths.