Six people have been arrested following a brawl involving hundreds of youths on London’s Hampstead Heath.
Police were deployed to the park at about 18:30 BST on Tuesday to disperse the crowd.
A dispersal order is now in place for the heath and nearby Parliament Hill, the Met Police said, and the public have been told to stay away.
Jonathan Jones, who had been at the heath at the time, estimated there were at least 50 officers at the scene.
“On the way into the park, we heard and saw police car after police car and police vans streaming by,” he said.
“We then got to the park entrance and three vans rolled in and there were a lot of police officers.”
Mr Jones said it was not clear what had sparked the brawl but he saw two girls being led away in handcuffs.
“It looked as if the police were trying to break up a fight, and then at some point, it looks like someone was trying to go for one of the officers.”
He added: “More police came really quickly, and they broke everything up, and then ordered everyone to leave the park.”
A Met Police spokesman said: “A S35 dispersal order is in now place for Hampstead Heath and Parliament Hill.
“Officers attended and the majority of people dispersed. No reported injuries and six people have been arrested.”