Police said on Friday a 16-year-old boy stabbed to death in a London street had been attacked by at least three male assailants armed with a baseball bat.

Shakilus Townsend died in hospital overnight after the attack in Thornton Heath, south London, on Thursday afternoon.

Police found him with a number of stab wounds in the entrance to a block of flats after receiving a call from a member of the public.

Witness Dee Bamina told Sky News Townsend cried out as he lay bleeding: "I don't want to die. I want my mum."

She said his last words before paramedics took him away were: "I cannot breathe."

An air ambulance flew Townsend to St George's Hospital in Tooting, but he was pronounced dead shortly after midnight.

Up to seven black youths had been in the area of the attack before the murder, Detective Chief Inspector Cliff Lyons told Sky News.

"I know that three particular individuals, males, attacked him with a baseball bat and attacked him with a knife," Lyons said.

He said one possible line of investigation was that Townsend was killed in a dispute over a girl, but added that police were keeping an open mind about the motive.

He did not think the attack was gang-related.

The killing follows a spate of murders of teenagers in the capital this year.

Another 16-year-old, Ben Kinsella, was stabbed to death in Islington, north London, last Sunday after a fight in a nightclub. Three teenagers appeared in court on Thursday charged with his murder.

His actress sister Brooke Kinsella, who appeared in "EastEnders", has appealed for young people to put an end to the violence that has plagued parts of the capital.

Deputy Metropolitan Police Commissioner Paul Stephenson said tackling knife crime was his force's number one priority.

He said Scotland Yard had set up a 75-strong anti-knife squad to target "known gang members and their associates."

London Mayor Boris Johnson has said he was shocked by the murders and had warned his children not to intervene if they see a fight in the street.

On Wednesday, police said they had arrested 1,214 people in London during a six-week crackdown on knife crime.