Mayor of London Boris Johnson said:
"It is heart breaking to see the life of another young Londoner taken so tragically. My thoughts are with this young man's family at such a terrible moment."
"This horrific incident serves as an unwelcome reminder that although violent crime in the capital continues to fall, we must continue our fight to tackle youth violence and get knives off our streets."
More top news
A woman who sparked a hate campaign against an ex-boyfriend and the women he dated has been jailed for stalking.
Surrey Police say they are working through more than 100 calls over reports a boy was 'abducted and bundled into van' in Redhill in Surrey.
Police have made a breakthrough in rape investigation using DNA and CCTV footage.