UPDATE: Sunshine Coast police are urging parents to be aware of where their teenagers are heading out at night after a number of assaults and robberies occurred at unsupervised parties on Coast beaches.
Detective Sergeant Brad McMeniman said the frequency of the beach parties and assaults had been increasing as the weather warmed up, with groups of up to 100 youths gathering on the beach between one and three times a week.
"Over the last month or so those parties seem to be happening more often," he said.
"The party-goers tend to range in age from 13 and 14 up to 18 and there's alcohol consumption, there's no police presence, no adult supervision and there's been a lot of assaults, robberies, injuries from dangerous acts with fire and with those parties being so close to the water there's also that risk too that we've got to take into account, so there's growing concern from us."
Det Sgt McMeniman said many of the parents whose children were attending the parties had no idea that they were even there.
"The parents aren't aware," he said.
"So we're asking the parents to sit down with your teenagers, find out what they're doing on a Friday or Saturday night and explain the dangers of attending these parties that are unsupervised.
"You may have all the trust in your child but there's other children there that are not handling the alcohol well, they're getting hyped up and there's been quite a number of assaults, robberies and injuries as a result. Innocent bystanders are being assaulted and have serious injuries as a result."
Det Sgt McMeniman said police would be focusing more attention to the beach at night on the weekends to prevent these parties from happening.
"Now we're aware of it we're increasing police presence and we've increased uniformed and plain clothed patrols up and down coastal strips to locate these parties," he said.
"We haven't had anything really serious happen yet because we've been lucky, I think that's the only reason we haven't. If these parties continue like this there's a very real risk that we will end up with a very serious injury at some stage."
EARLIER: Sunshine Coast police are cracking down on beach parties after a serious of "separate and serious incidents" in which teens have been "punched, kicked and robbed, a girl injured from something thrown on a bonfire and a boy knocked unconscious".
Sunshine Coast Child Protection and Investigation Unit (CPIU) officer in charge, Detective Senior Sergeant Phil Hurst, said the incidents stemmed from large-scale teen parties at on beaches at Wurtulla and Mudjimba.
He said officers had noticed a recent increase in the popularity of beach parties for youth in the area with an increase in assault and property offences.
One of these parties at Wurtulla beach on September 19 escalated as a fight allegedly broke between two girls and a boy was knocked unconscious.
It will be alleged the Bokarina boy, 15, who tried to break the fight up was grabbed around the neck, punched in the face several times and head-butted, and knocked unconscious.
He was taken to hospital for treatment to head and facial injuries.
Snr Sgt Hurst said footage of the alleged fight recorded on mobile phones was confronting.
"Violence is sickening, dangerous and never acceptable," he said.
"Any time a physical altercation occurs the results can be catastrophic.
"Too many young people have lost their lives to random and senseless acts of violence.
"Watching the video and seeing how many people were cheering and encouraging the fight was extremely disappointing."
At another party early in September a 15-year-old girl was burned on her leg, arm and head after a can of deodorant exploded when it was thrown on a fire.
On September 26 about 70 people - most believed to be teens and young adults - were gathered at Wurtulla Beach, where to exchange students were allegedly followed by seven teen males who confronted and threatened them, demanding cash, mobile phones and personal property.
One of the students, a 14-year-old boy, was allegedly pushed to the ground and kicked. He received injures to the face.
Four people, aged 14 to 18 years, were charged over the alleged attack.
Snr Sgt Hurst said parents and teens needed to be aware of the dangers involved in these late-night beach parties.
"These parties often seem to have little or no adult supervision, and any time this happens, when you have very large numbers of teenagers out late at night with some consuming alcohol, problems can occur," Snr Sgt Hurst said.
"Many of these incidents are happening at 8.30 and 9pm at night, not 2 or 3 in the morning.
"Some of our victims and offenders are aged as young as 14."