Four police cars have been rammed during a street racing event in Hamilton overnight.
Waikato police said they received reports of a large gathering of cars and people at the intersection of Horotiu Road and Great South Road, about 2.15am on Sunday.
Officers dispersed the crowd and the vehicles moved on, before converging near the Base in Northgate.
Inspector Neil Faulkner said the crowd became "increasingly hostile" and officers were "put at serious risk due to the violent behaviour of many of those involved".
In one instance, a vehicle allegedly reversed at speed towards a police car, which officers were standing in front of.
As part of the investigation, police were looking for "a vehicle of interest", and to identify and speak with the two people.
Faulkner said the behaviour was dangerous and it was fortunate no staff or members of the public were injured.
"Police 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."
Anyone with information or dashcam footage should contact 105 - the police non-emergency service - or Crimestoppers on 0800 555 111.
Faulkner said police had received information that there was to be an illegal street racing event focusing on Hamilton City, with a large number of people travelling in from Cambridge and Huntly to take part. He said there were large numbers of people at eight different locations overnight.
"We deployed some staff in terms of trying to mitigate the harm caused by that at the various locations where we sort of thought that they would be most likely to congregate with the intention of disrupting any activity and getting them to move on, which predominantly worked really well."
"And then as the night wore on, what we saw was some more organised criminal elements join that group and start to cause us some problems."
He said there had been an increase in illegal street racing events, dubbed the "Hamilton invasion", in the last couple of months, with three cohorts.
"The first is the illegal street racing element, which is your boy racers doing skids at intersections. And they do that because actually that's what they like doing. They like the adrenaline, the thrill of it all. They like their vehicles. Sort of an evolution from car enthusiasts."
"Secondly, we have the supporter element, which to be fair accounts for the majority of people that do go along to these events. They're sort of there to see what's going on, be part of it. Again, to get the adrenaline from what's going on in front of them."
"And then what we have seen coming into this more and more recently is the organised criminal element, which, to be honest, from what I saw last night, were very opportunistic to cause any harm they can if they had the opportunity. So that's the concerning part about all of it."