About 300 young people engaged in multiple fights in a Wānaka park last night.
Otago Lakes area police said they were called to Dinosaur Park about midnight after reports of fights.
"At least three serious assaults were reported, involving young people being knocked unconscious, along with numerous other more minor assaults."
Acting district commander Inspector Matt Scoles said it was disappointing that many of those present had alcohol.
"We know it's a time of year where lots of people are out celebrating and having a good time. But we need parents to make sure their young people are acting responsibly, knowing where they are and what they are doing," he said.
It comes as Waikato police on Wednesday said too many parents had no idea where their children were during New Year's Eve festivities.
Scoles said many of those in the Wānaka fight were from out of town.
"Please, keep track of your kids, and have a plan with them around how everyone is going to stay safe. We don't want to be knocking on your door at 2am telling you something serious has happened involving your teenager.
"I'm sure many parents would have been horrified to learn their teens had been putting themselves in danger, consuming excessive amounts of alcohol and engaging in violent altercations.
"It's extremely dangerous for all involved when we have young people drinking under the legal age and gathering en masse without any supervision," he said.
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