Protester numbers outside New Zealand's parliament swelled Friday as police scaled back efforts to clear anti-vaccine demonstrators involved in violent clashes a day earlier.

A festive mood prevailed at a makeshift tent settlement inhabitants have dubbed "Camp Freedom", with music and dancing as police looked on from behind barricades.

It was a stark contrast to the fiery scenes Thursday, when a phalanx of officers attempted to evict the protesters, arresting 122 people and using pepper spray to quell scuffles.

Wellington police described the hands-off tactics as a "measured approach", pointing to the presence of children among the crowd.

"Police are continuing to monitor and contain protest activity at parliament grounds," Superintendent Corrie Parnell said in a statement.

"Police have identified a range of different causes and motivations among the protestors, making it difficult to open clear and meaningful lines of communication."

Activists have been camped on the lawns of parliament for four days in a protest that began Tuesday as a copycat of a "Freedom Convoy" action by Canadian truckers in Ottawa.

The parliamentary precinct has been declared closed to the public but the measure has not been strictly enforced and the number of protesters on the lawns increased from about 250 to around 1,500 throughout Friday.

A protester named Carrie, who declined to give her surname, said the activists remained committed to their goal of ending vaccine mandates.

"The way the police handled us has shocked us all to the core," she told AFP.

"What they did yesterday was way beyond any of our expectations. Brutal, absolutely brutal."

New Zealand requires mandatory COVID vaccinations for people working in sectors such as health, law enforcement, education and defence, with those who refuse the jab facing the sack.

Proof of vaccination must also be shown to enter restaurants, sports events and religious services.