Home Secretary Priti Patel has condemned the "utterly vile" violence at a street party in south London, which left 22 police officers injured.
Scotland Yard said officers were confronted by a "hostile" crowd as they tried to break up a "block party" on Overton Road, Brixton, on Wednesday night.
A number of police vehicles were damaged, police said, while two officers required hospital treatment for their injuries.
Four people have been arrested for assault and public order offences and remain in police custody.
Condemning the violence, Ms Patel said: "These are utterly vile scenes.
"Just last weekend, the whole country came together to praise our heroic police officers for putting their own lives on the line to keep us safe.
"I'll be picking up with the Met Commissioner immediately."
Shocking images circulating on social media from the scene show officers being chased by men brandishing improvised weapons.
In one video, a man can be heard telling a group of officers to "back up" as he confronts them with what appears to be a sword.
Officers with riot gear were sent to the scene, but they were forced to back off as missiles were hurled by the crowd.
BCU Commander Colin Wingrove from the Met Police said: "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.
"An investigation into the incident is now taking place and those involved will be brought to justice."
Mayor of London Sadiq Khan also condemned the "completely unacceptable events" in Brixton and said he was in touch with the Met Police.
"Violence against the police will not be tolerated," he wrote on Twitter.
"Large gatherings during Covid-19 are deeply irresponsibly and risk others' lives."
