Police took action to disperse crowds causing “significant disruptions” at two unlicensed music events in south London on Saturday night.
Metropolitan Police said in a statement dispersal zones had been applied in response to events in Clapham Common and Tooting Bec Common.
The zones allow uniformed officers extra powers to order people to leave the area and not return.
Meanwhile, Northamptonshire Police said a man was arrested and up to 50 people moved on following a planned operation to prevent and disrupt an illegal rave near Wellingborough on Saturday night.
A 34 year-old man from Wellingborough was arrested on suspicion of criminal damage and public order offences and is currently in police custody.
The events continue a sequence of unlawful gatherings in London over the past four nights.
Seven people were arrested and two weapons seized by police at illegal gatherings over Friday night and Saturday morning.
The arrests include two people in Newham who were carrying a firearm and a “Rambo-style” knife respectively, the Met said.
Five people were arrested at another music event in Third Avenue, West Kilburn, including two for attacking police officers. The Met said two officers were injured but did not require hospital treatment.
It comes after Met Police Commissioner Dame Cressida Dick vowed to shut down events flouting health regulations.
Officers were called to Newham at 4.50pm on Friday after receiving reports from concerned residents about a sound system being set up in Hoskins Close by a large group of people.
Three more people were arrested in Third Avenue on suspicion of violent disorder, a breach of Covid health regulations and racially aggravated public disorder offences targeting officers.
Two other people were arrested at the same event for attacks on police – one for throwing a bar stool at an officer, who was uninjured, and the other for racially abusing an officer.
Commander Bas Javid, of the Met’s frontline policing team, said: “All of the events which took place last night were illegal and in breach of the Covid regulations. We had officers out across the capital working hard to disperse them.
“The vast majority of people who attended engaged with officers and moved away from the locations without issue. However, again, a number refused to leave and became violent. We have made it very clear this type of behaviour will not be tolerated and there are a number of post-event investigations now under way.”
He added: “Our officers have done a very good job in some very difficult circumstances. I applaud the way they have been able to tackle some difficult situations. The seizure of two lethal weapons overnight further emphasises why the dispersal of these events is crucial to protecting our communities.”