New Zealand rushed to track the source of a sudden return of the coronavirus as the number of new cases in its biggest city rose to 17 and officials warned more infections were inevitable, according to AFP.

National health chief Ashley Bloomfield said there were 13 new confirmed infections in Auckland, all linked to four family members, ending the country's record of 102 days without community transmission.

Bloomfield said among the new cases was a student at one of New Zealand's largest high schools, attended by more than 3,000 children.

Prime Minister Jacinda Ardern said there were likely to be more cases linked to the recent spike. “As with our first outbreak, things will get worse before they get better,” she said in a televised address.