WELLINGTON: New Zealand's Prime Minister Jacinda Ardern extended a nationwide lockdown on Friday as the number of COVID-19 cases in the country jumped and the outbreak widened beyond its largest city, Auckland, to the capital, Wellington.

New Zealanders had been living virus-free and without curbs until Ardern on Tuesday ordered a snap 3-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 Aug 24, saying that the outbreak had widened to other cities.

New Zealand PM warns virus outbreak will grow

"We just don't quite know the full scale of this Delta outbreak," Ardern said at the news conference.

Health authorities said 11 new cases were recorded on Friday, of which three cases were in Wellington.

The three in Wellington had recently travelled to Auckland and had visited locations that were identified as exposed to the outbreak, the health ministry said in a statement.

""We want the whole country on high alert right now," Ardern said.

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.

But her government is now facing questions over a delayed vaccine rollout, as well as rising costs in a country heavily reliant on an immigrant workforce.

Just about 19% of the country's 5.1 million population has been fully vaccinated so far, the slowest among OECD nations.