British police have said 15 officers were injured when disorder broke out following an unauthorised music event in the Brixton area of south London overnight.
The Metropolitan Police said they had been called to the street event but the crowd refused to engage with officers.
"The event continued and more officers attended the scene and the group became hostile towards officers," the police said.
Footage on social media showed a number of police vehicles being smashed and officers chased during clashes with a large crowd near the Angell Town estate in Brixton.
After what appeared to start as a street party, footage showed bottles being thrown at officers as the authorities were chased from the area.
Police said 15 officers were injured, none seriously although two required hospital treatment, and a small number of police cars were damaged.
Home Secretary Priti Patel described the images as "utterly vile scenes", and said she would be speaking to the Metropolitan Police Commissioner.
Four people are in custody after arrests were made for assault and public order offences.
"Last night we received numerous concerns from residents complaining about a large gathering, noise, anti-social behaviour and violence and officers responded to those concerns," said police Commander Colin Wingrove.
"These gatherings are unlawful, as well as posing a risk to public health and against coronavirus restrictions. The violence shown towards officers is totally unacceptable and we will not tolerate it in any form."