Criminals being monitored by electronic ankle bracelets are among the people attending the protest at Parliament, the Department of Corrections has confirmed.
In a statement, a spokesperson said Corrections was aware of a "small number of people" subject to GPS monitoring have attended the protest at some point in the past fortnight.
"We have reviewed the conditions of each person's sentence or order, and to date none appear to have been in breach of their location or monitoring conditions by attending."
Corrections was continuing to monitor the situation and remained in contact with police, the spokesperson said.
More than a dozen police officers with riot gear and protest security are making their way towards protesters - after violent clashes this morning.
About 14 officers with riot gear, accompanied by paramedics, are walking down Bowen St, towards the Lambton Quay intersection, followed by more than 30 police wearing protective glasses.
It comes after three officers were hospitalised after an unknown substance was thrown on them this morning and three people were arrested - including the driver of a car that drove towards police shortly after 6am.
At just after 4.30pm, some riot police were stationed on the footpath and others on the road.
Several people are frantically moving their cars, while about 200 people - occupiers and Wellingtonians - have started to crowd the area.
Two paramedics are also with police, indicating there is an expectation for conflict with protesters.
Police have positioned themselves in front of the two concrete bollards blocking the left turning lane from Bowen St onto Lambton Quay.
A forklift appeared to be repositioning the bollards, before leaving the scene - accompanied by officers running beside it - 20 minutes later.
Meanwhile, a man is urging people to stay calm over a loudspeaker: "Do not antagonise the police".
Some protesters have started a chant "love and peace" while others are linking arms along the concrete blocks.
Protesters say police had warned them in advance of the action and it had been announced on the main stage about10 minutes before they began.
At 4.50pm officers had moved well down Featherston St, near the Bunny St intersection.
Simultaneously, police were trying to ensure vehicle traffic keeps flowing and pedestrians, protesters and onlookers do not wander into traffic.
Riot police appeared to be heading back to base but turned around and have again congregated at the two bollards blocking the left turn from Bowen St onto Lambton Quay.
Protesters have again formed a human chain directly in front of riot police.
Traffic is backing up Whitmore St and Lambton Quay as the corner with Bowen St remains blocked during the police operation.
The northern end of Lambton Quay is still inside the protest zone but is sparsely populated.
A mixture of protesters and other members of the public are walking down Lambton Quay and a line of protesters is at the concrete bollard barricade.
They are yelling "love and peace".
The Prime Minister has joined police in condemning the "disgraceful" behaviour from protesters that saw three officers hospitalised this morning.
It follows an early morning police operation to move in on the occupation, now in its third week, after which a protester was arrested for driving a car into a crowd.
Speaking to media in Auckland, Jacinda Ardern said the attacks on police had been disgraceful.
"There are a group that are increasingly acting out in a violent way towards police officers who are only doing their job," she said.
To anyone who has said this is a peaceful protest, they could surely see now that in some quarters, it was not, Ardern said.