One youth has been arrested in Kingston on suspicion of carrying a balaclava, and his parents have been informed.
The incident happened near Fairfield Park moments ago, and one officer was heard to shout "you are not coming into Kingston with a balaclava".
Four police cars and a police van responded immediately to a group of youths heading from Cattle Market car park. Officers at the scene said Section 60 stop and search powers were being used.
Barcadia is the only licensed premises open in town, and police said they were about to ask it to shut.
Police at the scene phoned the youth's parents, who were not aware he was out and said to be very angry.