New Zealand has recorded 45 new community cases of COVID-19 in the past day, a sharp increase compared to the eight infections reported the day before.
This brings the total number of cases in the current outbreak to 1,230.
All new cases were in the biggest city, Auckland, which has been under lockdown for more than a month, although restrictions were eased slightly last week.
Director-General of Health Ashley Bloomfield urged everyone in Auckland to stay within their bubbles and wear face masks.
"This emphasises the importance of everyone in Auckland continuing to abide by alert level three measures," Dr Bloomfield said.
"They are there for a reason, and this includes mask wearing and importantly minimising contact with others, staying in your bubble as much as possible."
In August, genomic sequencing revealed the Auckland outbreak was linked to a traveller from Sydney who arrived in the country on a red zone flight and entered hotel quarantine.
Auckland was nearing the end of its first week under its downgraded level 3 restrictions, which were set to be reviewed on October 4.
New Zealand successfully contained the COVID-19 outbreak last year by restricting travel to returning residents and implementing a lockdown.
Its extensive testing and contact tracing operation was up and running by July 2020 and its elimination strategy was praised by the World Health Organization.
The country has pursued the strategy ever since, with the backing of residents who have largely lived free from COVID-19 restrictions for 18 months.
Now the Delta variant is posing a significant threat to countries once praised for keeping the virus out.
