Several campers were robbed and assaulted at Waterhall playing fields on the edge of Brighton at about 11pm on Friday.
The fields were being used as a temporary campsite for people coming to Brighton and Hove Pride.
One of the victims was assaulted with a police-style baton.
Sussex Police issued an appeal for witnesses to come forward.
Detective Constable Stewart Cameron, of the Brighton Anti Victimisation Unit, said: “This was a very distressing incident for the campers who were enjoying the carnival festivities.
“We believe the assaults were carried out by more than one person.”
One of the suspects is described as white, aged about 19, about 5ft 8in tall, with dark gelled curly or wavy hair.
He was wearing a black shiny tracksuit type jacket and dark coloured trousers.
Police are asking anyone with information to call 0845 6070999.
