Police were called to Hornsey Road, at 3.56pm today, and London Ambulance Service and London’s Air Ambulance also attended. The victim was found with stab injuries and is in serious condition in hospital.
A crime scene is in place and three men have been arrested, with enquiries ongoing.
MyLondon reported that forensics entered an address close by and removed items of clothing for further examination, before leaving the scene.
Footage from the scene also supposedly shows the victim being given CPR by paramedics.
A London Ambulance Service spokesman said: “We were called today (9 June) at 3.57pm to an incident in Newington Barrow Way, N17.
“We sent a number of resources including an ambulance, a medic in a response car, an advanced paramedic and an incident response officer.
“We also dispatched London’s Air Ambulance.
“We treated a man at the scene before taking him to a major trauma centre as a priority.”
READ MORE: London shooting – police on scene after shooting in broad daylight
“A 19-yr-old man died following the incident in #Hornsey Rise Gardens #N19 at 4:25pm on 8June.”
The attacks are the latest in a series of violent incidents in London.
Also in Islington, flower seller Tony Eastlake, 55, was stabbed to death earlier this month.
A 20-year-old man was subsequently arrested and charged with his murder.
A man in his early 20s was shot dead just miles away in Turnpike Lane in the early hours of Friday morning, with investigations ongoing.
And Black Lives Matter activist Sasha Johnson remains in hospital in a critical condition after being shot in the head at a party in Peckham in south London last month.
Speaking last month shortly after his re-election, Labour’s London Mayor Sadiq Khan vowed to make it his priority to drive down violent crime in the capital.
He said: “There are far too many grieving families in our city who have needlessly lost loved ones to violence.
“As I start my second term as mayor, I’m absolutely determined to drive down violent crime across our city.
“That means a relentless focus on being tough on crime by supporting our hardworking police officers to keep our city safe, as well as being tough on the complex causes of crime, like poverty, inequality and lack of opportunities for young Londoners.”