New Zealand's top cop says it was unnerving watching the "extreme violence" as police moved in on protesters occupying the area outside Parliament last Wednesday and that at moments, and it was "touch and go" for police. 

The operation began just before 6am on day 23 of the occupation when police moved to all of the key sites around the protest area, pulling down tents and clearing protesters and their vehicles. 

Police Commissioner Andrew Coster said on TVNZ's Q&A that he was incredibly proud of the police response to the situation, but that he didn't "take too much pleasure from the way things finished". 

"None of us wanted that kind of ending...but you would not see a more professional, restrained, courageous response to a situation then you saw there," Coster said. 

Police were confident in being successful after being able to reduce numbers and vehicles on the site, and moved in after talks with protest leaders to bring order to the protest failed. 

"The mix of the protest changed, we saw some of the original crowd leave and we saw people come in who appeared to be there for defiance and violence rather than the original issue," he said. 

"Eventually they declined into disorder and we could see we needed to act." 

More than 100 people have been arrested for offences ranging from willful trespass to obstruction. 

Coster confessed that watching the events unfold from the police command centre was "very unnerving". 

"The level of violence that we saw when people started lighting fires, and there were moments that were really touch and go," he said. 

"There was a particular moment where officers, about three lines of them, were being pelted with pavers from the footpath. They had their shields up and were being driven backwards...our commanders took the decision to use sponge rounds and that shifted the balance and allowed us to regain control." 

He said there had been a risk that the violence could have been driven to the shops and "who knows what damage would have been done". 

Coster said there was always a risk that the situation could have escalated to becoming a full-scale riot. 

In a scene filmed by a Newshub crew, it appeared to show a man may have been punched twice by a police officer and a few seconds later fell to the ground unconscious. 

Coster refused to comment on this incident, saying these would be looked into by independent investigators, but that he stood by his officers and remained "incredibly proud" of his people. 

"We will be investigating a lot of the things that had occurred, and the quite serious offences, the lighting of fires, the stoking of those fires, the throwing of projectiles at police," Coster said. 

Eight officers had been injured, mainly by protesters, but all were discharged within 24 hours. 

"Some head injuries from bricks, leg injuries from falling to a drain that had been opened up, there was a range of improvised weapons used," he said. 

Coster said substances had also been thrown at police. 

"No one wanted the situation to reach the point that it did...and I believe we need to think as a nation on what that means for us, how we got there and how we avoid being there in the future," he said. 

"It doesn't do to have sections of our community who are feeling so disconnected from everyone else."