A spokesman for the Metropolitan Police said no arrest has yet been made.
He said: "A murder inquiry is now under way and an incident room will open in due course under detectives from the Specialist Crime and Operations Directorate.
"We must retain an open mind re the circumstances of the incident and any motive at this early stage."
Anyone with any information can call police on 101 or contact Crimestoppers anonymously on 0800 555 111.
More top news
The mother of a former altar boy who tried to blow up a train insisted he was 'a big softie' who didn't want to hurt anyone.
Its current five year licence comes to an end next Tuesday.
Extra armed police will guard major sporting events in London this weekend after the military was drafted in to protect key locations.