WELLINGTON, Aug. 13 (Reuters) - New Zealand Prime Minister Jacinda Ardern said on Thursday (Aug 13) she expected the coronavirus cluster in the country to grow further before slowing down, as the Pacific nation reported an additional 13 new cases from domestic transmission.

"As we all learnt from our first experience with COVID, once you identify a cluster, it grows before it slows. We should expect that to be the case here," Ardern told a media briefing in Wellington.

The discovery of four infected family members in Auckland two days ago shocked a country that had not recorded a case of COVID-19 for more than three months.

Health authorities rushed to implement a rapid lockdown in the country's largest city Auckland, moving to alert level 3 restrictions from noon on Wednesday for three days.

Some of the everyday freedoms New Zealanders had enjoyed were taken away again. Gatherings in the city were restricted to a maximum of 10 people and Aucklanders have been urged to wear masks.

Nursing homes nationwide were told to shut their doors, with Ardern saying it was the best way to protect vulnerable seniors in facilities that have proved to be transmission hotspots overseas.

Ardern weighed delaying New Zealand's upcoming election on Wednesday as experts investigated whether the coronavirus could have re-entered the country through freight shipments.

Parliament was due to be dissolved on Wednesday to allow the election to take place, but Ardern held off the move until Monday to monitor how the crisis evolves.