Melbourne community festival Summersault 2017 has been plagued with assaults, thefts and more over the weekend, with The Age reporting between 30 and 40 teenagers stampeded through the crowds stealing mobile phones, throwing rocks and assaulting attending families on Saturday night.

Six people reported their mobile phones stolen and two reported being assaulted, Victorian Police said, while another attendee reported her 16-year-old son was hospitalised for a night after he was punched and had his phone stolen.

It's being reported that the 10pm fireworks display served as a distraction of sorts, as the group of teenagers ran through the Caroline Springs crowd while they filmed the fireworks.

Witness Joe Cuic said, "Out of nowhere, everyone's gone from standing there watching, having a lovely time, to people just running in all directions."

Melton City Council ran the alcohol-free event and Melton councillor Steve Abboushi said, "I'm really shocked and concerned at these reports."

Summersault Festival boasted headline sets from Sneaky Sound System, Nathaniel and Ash Grunwald before the mayhem during the event's finale.