Seven officers have been injured after police attempted to break up an unlicensed music event in west London.
Police were called to White City on Friday evening following reports of a number of people gathered at an estate.
Bricks and other missiles were thrown at police when they attempted to engage the group, forcing them to retreat before additional public order-trained officers arrived.
None of the injuries are said to be life-threatening, the Met Police said.
Officers trained to deal with public disorder who arrived on the scene to disperse the group were met with further hostility and violence, police said.
A Dispersal Zone has been authorised in the area while a section 60 order is also now in place.
Deputy Assistant Commissioner Laurence Taylor said seven officers had suffered injuries as a result of the clashes.
“Officers have responded to residents complaining about a 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.”
Police in the capital have been called in to break up a number of illegal gatherings in the past fortnight, with more than 20 officers hurt at a gathering in Brixton, south London, on 24 June.