Three arrests were made during marches on Parliament today by the extreme right-wing group the National Front (NF) and its opposition Multicultural Aotearoa (MCA).
However, police say the main problems came from a radical group who confronted the NF.
Police estimate about 45 NF members met in front of the Cenotaph by Parliament in central Wellington while 800 people marched with the MCA from Te Papa.
Inspector Paul Berry of Wellington police told NZPA about 200 members of a "radical, anarchist, punk-rocker type group" also converged on the Cenotaph .
After the march NF leader Kyle Chapman criticised police actions when the NF had trouble leaving but Mr Berry was unsympathetic.
"My job is to be impartial and let both groups protest within reason. I'm not there to baby-sit the National Front. If they want to come to town to protest it's up to them to find a way home. I'm not a taxi service."
An NF member was one of the men arrested, for possession of a knife and disorderly behaviour, after leaping on to his car bonnet with a wooden baton.
Mr Berry said the man was provoked by one of the radicals throwing a full beer bottle at the man's car.
Another radical protester was also arrested for disorderly behaviour and possession of a knife while the third was arrested for trespass at the police station.
"The radical group who confronted the National Front down at the Cenotaph really did cause most of the trouble," said Mr Berry.
"They had set out to confront the National Front people and make it their business to scare them out of town... we had a couple of bottles thrown from the crowd at either the National Front or into the police lines.
"We had a protester with a patu -- a Maori club, a wooden one -- hit a National Front member in the head."
Mr Berry said the NF mostly did what police told them to do but could have been "more sensitive to their plight... most of them managed to contain themselves despite quite nasty verbal attacks".
He said the 45 police on duty were sufficient although a few more might have helped.
One police officer was cut by glass when a glass bottle thrown shattered on a car and glass hit him in the hand.
NF director Mr Chapman earlier said he had expected about 150 supporters to rally in favour of free speech and of keeping New Zealand's current flag.
MCA, formed in response to recent racist activity in Wellington, on its website said its three aims were to "stop the National Front, oppose humiliating immigration policies and stop Maori bashing".
They had expected up to 3000 marchers