Police are threatening to confiscate mobile phones in Bournemouth this weekend in a clampdown on so-called happy slapping attacks.
Anyone they suspect of using a phone to arrange or to video acts of violence will have the device taken away.
Supt Stuart Katon said: "Anyone coming into Bournemouth ... with the intention of causing trouble should be aware that this behaviour will not be tolerated."
Videos of the attacks are recorded on the mobile and posted to websites.
"I am appealing to parents to make sure they are aware of their children's plans and to make sure that they are not given alcohol to go out with or allowed to consume alcohol before they go out," he said.
"The last thing we want to do is call you to say your child is in custody."