Police say a 16-year-old boy was stabbed to death in the street after one of the people he was with attempted to rob two other youths.
Ashley was stabbed to death in Upton Park
They believe Ashley Hedger from Upton Park, east London, was killed after one of the youths went into an Islamic centre and emerged with a group of men.
Police do not believe the murder was racially motivated.
They are appealing for anyone with information about Friday's incident to come forward.
Ashley, who is white, was in a group of five white and black youths when he was attacked at about 1300 GMT in Plashet Road, Upton Park.
A post mortem examination established Ashley died of multiple stab wounds.
Scotland Yard said investigating officers had yet to make any arrests.
Detective Superintendent Maureen Boyle, who is leading the inquiry, said: "This was a spontaneous incident, the catalyst of which was the attempted robbery, which has led to tragic consequences.
"This is a very close knit community and whilst we have had a great deal of support and assistance from the community we would appeal to anyone who was in the area, anyone who witnessed anything, or anyone with information to come forward."