New Zealand's Prime Minister Jacinda Ardern has extended a nationwide lockdown as the number of Covid-19 cases in the country has jumped and the outbreak has widened beyond its largest city, Auckland, to the capital, Wellington, Reuters reports.

New Zealanders had been living virus-free and without curbs until Ardern, on Tuesday, ordered a snap three-day nationwide lockdown and seven-day shutdown in Auckland after discovering the country's first case since February.

Ardern has extended the lockdown until midnight on August 24, saying that the outbreak had widened to other cities.

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