Gorseinon planned gathering warning from South Wales Police
Police have urged parents to help keep young people out of trouble after officers became aware of a gathering being planned for Monday.
South Wales Police said it was being planned for Gorseinon, Swansea.
Insp Jay Davies said parents may think children are doing nothing wrong, but they could be breaching Covid-19 regulations with the impact of behaviour "significant".
He said 400 youths congregated for one unauthorised gathering in July.
"We would like to make it clear - underage drinking, fires causing criminal damage, fighting and foul and abusive language is all antisocial behaviour and this will not be tolerated," he said.
He said patrols would increase on Monday evening with officers working alongside British Transport Police to find those arriving by train.
There have been a number of gatherings in the force area this summer, including at Cardiff Bay where dispersal orders have been put in place, and at Ogmore-by-Sea, which ended in violent clashes and a mass brawl.
Large groups have also been dispersed from a number of Gower beauty spots.