New Zealanders had been living virus-free and without curbs until Ardern on Tuesday (August 17) ordered a snap three-day nationwide lockdown and seven-day shutdown in Auckland after discovering the country's first case since February.
Ardern extended the lockdown until midnight on August 24, saying that the outbreak had widened to other cities.
Health authorities said 11 new cases were recorded on Friday, of which three cases were in Wellington.
New Zealand's health chief, Ashley Bloomfield, warned the lockdown in Auckland, the epicentre of the outbreak, may be extended further.
Ardern has won praise for containing local transmission of COVID-19 via an elimination strategy, imposing tough lockdowns and shutting New Zealand's international border in March 2020.