Sussex Police said nine people were arrested for offences, including assaulting an emergency worker.
Sussex Police said an officer was receiving hospital treatment for a 'serious cut to the face'Sussex Police said officers were called to King George Field in Mayfield, East Sussex, by a private security firm on Saturday night.
Nine people have been arrested on suspicion of a number of offences including assaulting an emergency worker and public order offences.Det Supt Miles Ockwell said: "As officers sought to make an arrest, they were attacked by a group of young people and had to deploy incapacitant spray to try to defend themselves.He added a dispersal zone was in place in the area preventing groups from "gathering and committing offences".