The man, from France, was stabbed in the chest in the early hours of Saturday by four men who left the scene in a white car, thought to be a Vauxhall.
Scotland Yard's racial and violent crime task force, led by Deputy Assistant Commissioner John Grieve, has been called in to supervise a team of detectives at Holloway police station, north London, near to where the attack happened.
The man, who is not being named by the police, was attacked at the junction of Holloway Road and Kingsdown Road as he walked home with a friend, also male and black. His condition last night was described as critical; his friend was said by police to be in deep shock.
"We are treating this as a racial crime," said Chief Superintendent Ron Hope. "We are looking for four white men and we are appealing for witnesses to come forward. We are determined to do everything we can to trace and arrest those responsible."
A Scotland Yard spokeswoman said officers had succeeded in tracing the victim's family. Detectives are refusing to reveal his identity or the location of the hospital in which he is receiving treatment. He is thought to be in his twenties.
Police yesterday issued a description of their "main suspect", although they refused to say whether he was the one who used the knife. He is aged about 28, 5ft 10in with a slim build and short, black, slightly curly hair. He was wearing a white shirt with a white vest underneath, black jeans, black shoes and a black raincoat.
After the attack, all four men ran to the white car and drove off. The police were called at 2.05am by a member of the public.
The investigation is being seen as the first serious test of the Metropolitan Police's anti-racism resolve, which came in response to severe criticism of its handling of the Stephen Lawrence case. Stephen, an A-level student, was stabbed by a gang of white men in Eltham, south- east London, in 1993, also in the company of a black friend.
The racial and violent crime task force has already earned some credibility by bringing charges over the killing of Michael Menson, a black musician who was set on fire in Edmonton, north London, in a racist attack. A Turkish Cypriot man will go on trial in northern Cyprus next week for his murder.Reuse content