Another London stabbing occurs
UPDATE: 6:59PM EST
Some more details about the stabbing have emerged:
According to witnesses the boy, believed to be as young as 14-years-old, was chased by at least six hooded and masked youths before being knocked to the ground and knifed in the chest four times.
Although witnesses say the victim was in his early teens, both the police and the ambulance service have said he is in his early 20s.
The attack happened in Beluah Crescent, Thornton Heath at around 1.46pm this afternoon.
Eyewitness, Richard Higgins, 17, was shaken by the ordeal.
He said: "The first thing I saw was loads of blood. I heard the boy crying for his mum over and over again. Even when the ambulance came he was trying to take off the oxygen mask and speak to the ambulance crew to tell them to call his mum."
Police recovered the knife used in the attack after witnesses saw the assailants throw it into a bush. Both the bush and the knife were covered in blood.
Mr Higgins added: "The boy couldn't have been any older than 14 or 15 he was tiny and looked terrified."
Residents described how a group of five to six black males and a mixed race female, dressed in hooded tops with scarves and balaclavas chased the boy through around Beluah Crescent on pushbikes.
Residents said they heard the youths shouting "Get him, he's over there" before chasing him down outside a block of flats. They pounced on the boy stabbing him four times in the side and once in the centre of his chest.
Retired Peter Gibbs, 60, said: "I have asked for more patrols and they never listen. There was as shooting around here last time and nobody came.
"It's a disgrace. I've seen gangs around and I am afraid. I want the police to do something about it but nobody helps. I feel terrified and so do the other residents. it's just not good enough."
A London Ambulance Service spokesperson confirmed they sent a fast response car, an ambulance and an air ambulance to the scene.
A man in his twenties is fighting for his life in hospital after becoming the latest victim of London's knife crime spree.
Police and paramedics were called to an incident in the Beulah Crescent area of Thornton Heath, in the south of the capital.
The victim has been taken to an undisclosed London hospital.
He is said to be in a critical condition, with life-threatening injuries.
At this stage, police have not released any details of the suspect, or suspects, they are looking for.
But they confirmed there have not yet been any arrests.
More information to come.