One man, aged 20, is fighting for his life in hospital after the attack in Rosebery Avenue, Islington at 10.10pm on Friday.
Two suspects, thought to be men or teenage boys, are believed to have fled down an alleyway towards St John’s Road and then onto Wyclif Street.
Armed officers rushed to the scene and found another 19-year-old with not life-threatening injuries.
DI Darren Jones, who is leading the investigation, said: “This is a fast-moving and complex investigation. We are doing everything we can to track down the person, or people, responsible for this awful attack. My thoughts are with the victims and their families at this time.
“Our initial enquiries suggests the pair were attacked by two suspects, who are thought to be men or teenage boys. They left the scene down an alleyway towards St John’s Road and then onto Wyclif Street.
“I would ask anyone who was in the area at around the time of the incident, and say any suspicious activity, to contact us immediately.”
Anyone with information that could assist the investigation is asked to call 101 quoting CAD 7488/09Sep. To remain anonymous contact the independent charity Crimestoppers on 0800 555 111. No arrests have been made.