Nelson police arrested five teenagers on Wednesday night in Victory Square after a party got out of hand on Vanguard St.
Police received a number of calls from concerned residents around 10pm after drunk youths spilled out of the party on to the street.
A police spokesperson said residents alleged a security guard doing noise control and other members of the public were assaulted.
Sergeant Shane Miles said no one was seriously injured in the assaults but three people were treated by ambulance staff at the scene.
The five people arrested, all under 20, spent the night in police custody and will face disorder and assault related charges in the Nelson District Court.
"This incident had the potential for someone to have been seriously injured and was a perfect example of why unsupervised youth parties involving alcohol are bad idea," Mr Miles said.
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