A teenager has been stabbed to death during a fight between a group of youths in south London.
The 15-year-old was with friends when they were surrounded by another group in Black Prince Road, Lambeth, on Thursday night, police said.
A row erupted between the two groups and the boy suffered a single stab wound to the left side of his chest.
Police say they want to trace 10 black youths, in their teens, who were wearing dark clothing at the time.
The victim, who police say is from a Christian family, was taken to St Thomas' Hospital by a member of the public but was pronounced dead shortly after midnight.
Det Supt Richard Heselden said after the verbal altercation between the two groups, the larger group left the scene and returned armed with various weapons, including baseball bats and hockey sticks.
At least two knives and a claw hammer have been recovered from the scene and forensic tests are being carried out to determine whether they are linked to the incident.
Police said the motive for the attack is unknown.
"You have a 15-year-old who had everything to live for who is now no longer with us," said DS Richard Heselden.
"It's another tragic incident and I would urge people not to carry knives."
Police are conducting a forensic examination of the area and carrying out house-to-house inquiries.
Officers are also checking to see if the incident was captured on CCTV cameras.
"It was a warm summer evening and we are sure the streets would have been busy at the time of the murder," DS Heselden added.
A mobile police station will be deployed to assist with the inquiry and patrols will be stepped up to offer reassurance to the public.