A 16-year-old boy has been injured after he was allegedly attacked by a brazen gang of youths at a family-friendly music festival in Melbourne last night.

The large pack of offenders burst through the Summersault Festival in Caroline Springs around 10pm during a fireworks display.

“It was just this great big mass of people moving through. It was like a stampede. It was awful,” a witness told 9NEWS.

Jack Tesoreiro, 16, was knocked out and was one of six people who had their phone stolen during the incident.

Jack’s mother, Debbie, said her son had been walking a female friend to her mum’s car when he was attacked.

“He didn't know where he was, or what had happened to him,” Mrs Tesoreriro said.

Jack was taken to hospital suffering memory loss and a sore jaw, and is undergoing scans.

Another teenage boy, Darcy Franksen, was robbed of his backpack.

“I was like pretty scared at this point and then they actually chased me down and for the bag,” Darcy said.

“They took what was inside and there was $50 in there which they took from me.”

A total of six people had their phones stolen in the attack, police said.

Witnesses have described the group of alleged offenders as predominantly male with an African appearance.

Melton City council has stressed protective measures were in place throughout the event.

"Security and police were present on site for the duration and until large crowd numbers vacated the event," the council said.

Police investigations are ongoing.