Two police officers suffered broken bones after bricks and bottles were thrown when police attempted to break up an illegal rave involving suspected gang members on a London housing estate.
Seven officers were injured when police were called to disperse crowds in White City, west London, on Friday night following reports of disturbances at a block party in Havelock Close shortly after 10pm.
Witnesses claimed more than 200 Metropolitan Police officers dressed in riot gear were involved with clashes with revellers, who threw a barrage of missiles including bricks, rocks and bottles.
Footage circulating on social media shows dozens of officers retreating from the estate as large crowds of youths advanced on them in the streets.
Scotland Yard said no arrests have yet been made, although inquiries are underway.
London Mayor Sadiq Khan condemned the attacks on police at the event as "disgraceful".
He said: "Violence against the police will not be tolerated and perpetrators will be caught and prosecuted.
"Extra police will be out today continuing to work hard to keep our city safe."
Hammersmith and Fulham Police said it had received information about planned unlicensed music and barbecue events taking place across various locations in the borough hours before the incident.
“Intelligence suggests that these events will be attended by West and South gang members. This has previously led to violence and disorder," police said.
They released a map showing areas that would be affected by a Section 60, which allows frontline officers to search suspects without grounds, from 3pm on Friday to 6am on Saturday.
The incident is the latest involving police officers coming under attack at mass gatherings - despite the lockdown and fears of the spread of coronavirus.
Police leaders described how officers faced a “volley of anger and hatred” after a street party in Brixton on June 25 degenerated into violence, with missiles thrown and police vehicles attacked.
Three people who were arrested for violent disorder against police at the Brixton event have since appeared in court, and are awaiting sentencing or further trials.
Deputy Assistant Commissioner Laurence Taylor said officers were responding to complaints from residents about the large gathering, noise, anti-social behaviour and violence.
He said: “These gatherings are illegal and also pose a risk to public health.
“The violence shown towards officers this evening was totally unacceptable and we will not tolerate it in any form.
"Officers encountered bricks and other missiles being thrown at them. Our robust police response demonstrated that we will police incidents like these firmly and stop those intent on causing harm or disruption to our communities.”