The 15-year old boy was taken to hospital and is currently in a life-threatening condition. Met Police said they were called at 6.50pm to Harbour Avenue in southwest London.
Two male suspects have been arrested in connection with the crime, police said.
A Section 60 stop and search power has been authorised in the SW10, SW6, SW5 and SW3 areas until 7am on May 6.
This is a breaking story. More updates to follow…