South Wales Police is investigating an incident of disorder which happened at Ogmore-by-Sea in the Vale of Glamorgan yesterday evening.
Groups of people descended on the area throughout the afternoon and evening which culminated in large-scale disorder.
An investigation into the incident is underway and officers are appealing to witnesses and anyone with mobile phone or dash-cam footage to come forward.
Videos of the brawl that took place yesterday have been widely circulated on social media.
Detective Chief Inspector Tom Moore said: “The scenes at Ogmore-by-Sea were totally unacceptable and the main focus of our investigation will be to identify those who were responsible.
“We believe that a large number of youths have travelled to the area from various areas of South Wales to become involved in serious, violent disorder.
“I am appealing to anyone who can assist our investigation to contact us so we can identify and take action against those involved.
“The local community can also be assured that we will be working with partner agencies and doing everything we can to ensure there is no repeat of this behaviour.”
Anyone with information should call police on 101 or Crimestoppers anonymously on 0800 555 111 quoting occurrence number 2000225710.