A 14-year-old boy died in hospital today from injuries suffered in a stabbing in central London nearly three weeks ago.
David Idowu, of Southwark, died at Royal London Hospital in Whitechapel, the Metropolitan Police said.
The teenager was stabbed in Great Dover Street, SE1, on 17 June after a row with a gang of youths in a nearby street.
His death brings the number of teenagers killed in London this year to 19.
Detective Inspector Bernie Galopin, of Southwark CID, said officers from the Met's Homicide and Serious Crime Command will now handle the murder inquiry.
He said: "Nearly three weeks after the attack on David, he has lost his life, and this will now be a murder investigation.
"In light of David's death, our immediate thoughts are with his family and friends and getting justice for them.
"I would like to take this opportunity to appeal to anyone who has information or who witnessed the attack but have yet to contact the police to come forward."
David is believed to have suffered two wounds, one to his stomach and the other to his chest.
He had earlier been involved in an altercation with youths in nearby Tabard Street.
Officers examined CCTV footage from halls of residence as part of their investigation into the incident.
Anyone with information is urged to contact Walworth CID on 020 7232 6145 or Crimestoppers on 0800 555 111.