Suspected gang members have been arrested in raids as police made a "robust" response to a spate of stabbings.
Eight south London addresses were targeted in relation to street attacks, including the murder of 17-year-old Kwame Ofosu-Asare.
Four male youths are being questioned for conspiracy to commit grievous bodily harm unrelated to the death of Kwame, in Brixton, the force said.
Chief Superintendent Matt Bell said: "Lambeth borough is committed to reducing serious youth violence and gang activity and we felt it vital that we take robust and prompt action in order to pre-empt any potential future violence."
Teenager Kwame was discovered on early Friday evening with stab wounds in Adelaide Close, Moorlands Estate, Brixton. He and a friend were chased by two knifemen, police said.
Officers were investigating if the killing is linked to another stabbing on Friday when a 17-year-old boy was attacked outside Norwood bus garage, Ernest Avenue, West Norwood at around 1.15pm.
There were also a number of gang-related street attacks in Lambeth on February 25, the force said.
The dawn raids were carried out across Lambeth where six other attacks took place.
Mr Bell said: "I want to reassure the community and the wider public that detectives are working around the clock to gather evidence and find those responsible, whilst extra patrols have been stepped up in the borough to act as a strong deterrent to anyone thinking of committing further violence in the aftermath of these incidents."
Anyone with information should call the incident room on 020 8721 4205; if you wish to remain anonymous call Crimestoppers on 0800 555 111.