The victim was fatally attacked outside a branch of Foot Locker in Oxford Street, at the heart of London's West End shopping district.
Witnesses said the black man, aged in his late twenties or early thirties, was involved in a clash with a group of other young men.
© Jenny GoodallFatal stabbing: The scene outside Foot Locker in Oxford Street where a man was stabbed to death on Boxing Day.
© London News PicturesWeapon? A knife lies on the floor, moments after the attack.
A bloodied silver lock knife was recovered after it was discarded in the street nearby and several men were arrested.
Traders in the West End have reported £15million sales in the first three hours of the Boxing Day sales today despite a drivers' strike on the London Underground.
Eyewitnesses said at least one of the arrested men also appeared to be injured and was lying semi-conscious on the floor.
One said: 'There were hundreds of people around and some panicked when they saw armed police officers running through the crowd.'
Eyewitnesses said stores inside the large police cordon were forced to close as shoppers were told to leave.
© GoogleThe man was killed on Oxford Street near the junction with Stratford Place.
© Agency France Presse/Getty imagesCrowds: The terrifying incident took place on Oxford Street, which today has been overflowing with shopper at the Boxing Day sales.
'We are being quite badly affected, we are unlikely to open again today.'
The employee said a number of shops in the area were closed including Boots, H&M and the Body Shop as the cordon continued west along Oxford Street towards Selfridges.
Police have shut down part of Oxford Street, close to its junction with Stratford Place, near Bond Street, after the stabbing which took place at 1.45pm.
A Metropolitan Police spokesman said: 'Six arrests have been made. Oxford Street has been closed around the scene.'
A man was knifed to death on Oxford Street three-and-a-half years ago in front of horrified shoppers.
Steven Bigby, 22, had been charged with raping a 16-year-old girl and was on bail when he was knifed to death in May 2008 close to the Oxford Circus station.
© London News PicturesProbe: Police swoop after a man was knifed to death outside Foot Locker today.
"A man was knifed to death on Oxford Street three-and-a-half years ago in front of horrified shoppers. Steven Bigby, 22, had been charged with raping a 16-year-old girl and was on bail when he was knifed to death in May 2008 close to the Oxford Circus station."
The quite affable, non-criminal brother of the 22 year old in question actually works at my work-place. Bizarre connections everywhere you look.