At 10pm police were called to respond to a party that was spilling onto the streets in Edinburgh St, Deeragun.
The 15-year-old boy who hosted the party was smashed in the eye with a full can of alcohol after confronting some unwanted guests.
Inspector Mark Jackson said this sparked a series of melees that took police three hours to completely dissolve.
"That series of events included several fights among different factions that had been at the party and assaults on various attendees," Insp Jackson said.
"(The host) suffered an injury to his eye that resulted in him being transferred to hospital.
"There was a car damaged nearby … as we understand one of the party attendees was trying to escape another group of attendees and took refuge in a car which wasn't his own and the people chasing him damaged that vehicle."
Insp Jackson said witnesses reported between 30 and 40 people involved in fights and responding officers remained at the scene until 1am.
He said uninvited people attending parties could be a recipe for disaster.
"We encourage people who are organising a party, particularly with teenagers or youths involved, that they plan for it and they have in mind that things can go wrong," Insp Jackson said.
"We encourage people to keep control of the party, not let in people who aren't invited and to contact police at an early stage if you've got people who won't leave."
Police are keen to speak with witnesses and anyone with information on the incident should call Crime Stoppers on 1800 333 000.
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