Three vans full of police officers were deployed to the park in north London at around 6.30pm to disperse the crowd. A helicopter was also deployed to the area to report on developments from the air.
One witness told the PA news agency there were at least 50 officers at the scene.
Jonathan Jones, who was at the heath with his partner for exercise, said: “On the way to the park, we heard and saw police car after police car and police vans streaming by.
“We then got to the park entrance and three vans rolled in and there were a lot of police officers.”
He said it was unclear what set the brawl off, but he saw two young 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.
“More police came really quickly and they broke everything up, and then ordered everyone to leave the park,” added Mr Jones.
Met Police Camden tweeted: “A S35 dispersal order is in place for Hampstead Heath and Parliament Hill. Please don’t attend these locations.
“We were called at 6.30pm to youths fighting in Parliament Hill. Officers attended and the majority of people dispersed. No reported injuries and 6 people have been arrested.”
A S35 dispersal order is in place for #HampsteadHeath & #ParliamentHill. Please don't attend these locations. We were called at 6.30pm to youths fighting in P'ment Hill. Officers attended and the majority of people dispersed. No reported injuries and 6 people have been arrested— Camden Police (@MPSCamden)June 2, 2020
Sergeant John Hounsell, who was one of the first officers at the scene, told the Camden New Journal there were no serious injuries but “police officers were assaulted during the incident”.
He said: “We had reports of young people drinking in separate groups but officers were on the Heath initially responding to reports of a robbery when we heard that a fight had broken out.
“it was 50/50 girls and boys but it was mainly girls fighting.”