Safety measures are being stepped up in Cardiff this weekend after concerns over "planned gatherings of youths".
Police are increasing patrols in the city centre, after being alerted to social media posts.
A spokesman from South Wales Police said: "We'd like to thank the public who have already made us aware of these posts.
"Any anti-social or illegal behaviour will not be tolerated and dealt with robustly."
It comes after increased police powers to stop and search people without suspicion were issued last month in Cardiff.
A 24-hour section 60 order was authorised after two "isolated and unrelated" stabbings in the city.