Riot police are on the streets of Brixton in a bid to stop a repeat of last night's violence which saw gangs of youths smashing windows and looting shops.
Violence broke out in the south London district following a peaceful demonstration yesterday against the fatal shooting by armed police of a man carrying a gun-shaped cigarette lighter.
A police spokesman said: "We have been closely monitoring the situation throughout the day.
"We are going to have high visibility patrols to let the public know we are around to allay any fears."
He said riot police would be on stand-by for trouble adding there were no planned protests this evening.
Trouble flared up after a protest against the shooting of parking attendant Derek Bennett, 29, who was gunned down in Brixton on Monday.
But at around 9pm last night, a gang of around 40 youths began smashing windows and looting shops, including Morley's department store.
The numbers later swelled to around 100 and senior police officers labelled the violence "mindless vandalism". They said a small number of youths had exploited the earlier protest outside Brixton police station.
A male Pc suffered head injuries and a woman officer had serious cuts to her arm, he added.
Police were tonight continuing to question the 27 people who were arrested.
Meanwhile, the inquiry team investigating the killing of Mr Bennett were today visiting the scene to question witnesses.
The Police Complaints Authority, the body which investigates police conduct, has brought in officers from Northumbria Police to establish whether the Metropolitan Police firearms team was to blame for the death.
They were today and tomorrow making house-to-house inquiries in the area around where Mr Bennett was shot six times.