Police have arrested two people and impounded six cars after a gathering of more than 200 cars in Levin on Saturday night turned violent.
The mayor says the community is "disgusted" by the incident, which was "very difficult" for police to control.
Manawatū area commander Inspector Ross Grantham said police were pelted with rocks and bottles, which injured two officers and damaged two police cars, during the "anti-social road user activity".
Six cars were impounded, one person was arrested for disorderly behaviour, and another - who was allegedly found with a flick-knife - was arrested for obstruction.
"Around 30 police staff, deployed to the area pre-emptively, were put at serious risk due to the aggressive behaviour of many of those involved."
More than 200 cars - each containing multiple passengers - began gathering in a carpark on Bath Street around 8pm Saturday.
The car convoy then converged at the intersection of Queen Street and State Highway 57, before attempting to do burnouts there, police said.
"Police staff managed to disrupt the activity and move them on, but not before patrol cars were kicked by bystanders, who also threw bottles at the cars."
The group then moved to Miro Street in Ōtaki, where they did more burnouts, Grantham said.
"Police chose to avoid actively engaging at this location, given it was an industrial cul de sac which would have posed further risk to our staff."
He said the convoy went back to the intersection of State Highway 57 and Tavistock Road in Levin, where they blocked the road and did more burnouts.
"A police patrol attempted to drive through the group to disrupt them, however the observing crowd turned on the officers, kicking and bottling the car."
The side window of the patrol vehicle was smashed, he said.
Police again dispersed some of the traffic, but the convoy moved to the intersection of Queen Street and State Highway 1, where officers armed with protective shields attempted to disperse the crowd.
"When officers turned into Oxford Street, the crowd had grown significantly and turned violent. People threw bottles, rocks, and bricks at the retreating police."
Two officers received minor injuries from items hitting their legs.
"A man arrested during this time for disorderly behaviour was allegedly wearing a stab-proof vest and carrying a large knife.
"This is incredibly concerning, as it indicates that the crowd was not just car enthusiasts, but included people out to deliberately provoke, aggravate, and endanger."
Police withdrew, but continued to monitor the burnouts from a distance and took footage of the activity in order to follow up on illegal behaviour, Grantham said.
"Police absolutely understand the stress and concern illegal and anti-social street racing causes members of the community, and we are committed to disrupting this activity by breaking it up when it occurs, and holding offenders to account.
"However, this is an example of how incredibly dangerous these situations can become, and I'm very proud of my staff who put themselves in harm's way.
"Police go to work every day to help make our communities safer, and behaviour such as this which prevents officers from doing so is entirely unacceptable."
Officers would be using CCTV footage and other information gathered at the time to follow up any criminal offending.
Anyone with information on illegal or unsafe activity should report this via the 105 Police Non Emergency website or by calling 105.
Horowhenua mayor Bernie Wanden said he was "disgusted" by the violence and disorder.
He said there was minor damage done around the town, including rope fences removed at a park to let cars in to do burnouts, and rubber marks on roads and roundabouts.
Car meets did happen occasionally, but things did not usually escalate, he said.
"As for the violence and the disorder, this is, for sure, out of the ordinary, and something that we're pretty disgusted as a community having had to put up with."
He said police were forewarned and did their best to put a stop to the behaviour early, but "they could do no more than they could".
The number of people and cars made it "very difficult to control", he said.
"We understand that they like to get together and do a few burnouts, but for this then to turn into action against the police and the community, it's very sad."