The attack in broad daylight Monday terrified shoppers on Oxford Street who were shuttled and locked into nearby stores as police responded to the incident, The Mirror reported.
Police said the stabbing was thought to have occurred directly in front of a Footlocker store near Bond Street London Underground Station.
Responding police cordoned off a section of the street, full of thousands of shoppers in the area for annual Boxing Day sales.
"Officers, London Ambulance Service and Helicopter Emergency Medical Service attended the scene. The male, believed to be in his late teens/early 20s, has been pronounced dead at the scene," a police statement said.
"A number of arrests have been made. Inquiries continue. Oxford Street has been closed around the scene," police said.
The victim's death occurred as Britons were projected to spend $2.8 billion in after-Christmas sales at the major London shopping locations of Oxford Street, Regent Street and Bond Street, The Mirror said.