Police officers have been attacked while attempting to disperse crowds at an illegal party for the second night in a row.
The Met Police said objects were thrown at officers at an “unlicensed music event” in Notting Hill, west London, in the early hours of Friday.
A witness said there were “about 150-200 people” present with violence breaking out from about midnight.
It comes after “appalling scenes” of violence at a street party in Brixton.
Malcolm, who has lived in the area for 10 years, told the BBC scores of people had gathered at the corner of Portobello Road and Blenheim Crescent from about 21:00 BST.
“After midnight it seemed to switch into more violent behaviour,” he said.
He added it had been “pretty terrible round here” for the last few nights with “anti-social behaviour, alcohol, drugs and a huge amount of violence and disruption”.
Kensington and Chelsea Police tweeted that objects had been thrown at officers dispersing the crowd at the event near Colville Gardens.
“Violence will not be tolerated and units are responding appropriately,” the force said.
The Met later said most people had dispersed from the area by 02:00 and there were no confirmed reports of serious injuries.
Commissioner Dame Cressida Dick condemned the “utterly unacceptable” behaviour.
She said the force had been on the lookout for unlicensed music events across the capital on Thursday evening and had “closed down several before they even got going”.
“These events are unlawful. They shouldn’t be happening and we have a duty to go and close them down and to disperse them,” she said.
One gathering took place on Streatham Common.
Lambeth Police tweeted that officers had “engaged with a large number of those in attendance and the crowd has now almost entirely dispersed”.
Another event was shut down in Mitcham, according to the force.
Home Secretary Priti Patel said the violence seen in some areas was “appalling”.
She added the police “have my full backing in tackling criminality and enforcing the law”.
On Thursday evening, Scotland Yard said it was undertaking an “enhanced policing operation” across the capital to ensure there was an “effective and prompt response to any reports or disorder”.
Commander Bas Javid said the move was “in direct response to concerns expressed by our communities, many of whom were scared and shocked by the events taking place outside their homes”.
Extra police officers in protective gear were dispatched following “appalling scenes” of violence at a street party in Brixton on Wednesday.
Scotland Yard said it was targeting further unlicensed music events and block parties around the city after 22 officers were injured on the Angell Town estate.
Footage on social media showed police vehicles smashed and officers pelted with bottles during clashes with a large crowd, with Downing Street condemning the scenes as “appalling”.