A 15-year-old boy has been stabbed to death following a birthday party at a community centre in Romford, attended by more than 100 people.
Officers were called to Clockhouse Lane at 9.05pm on Saturday following reports of a large fight following a birthday party, with early reports suggesting that groups were fighting and the centre was being damaged by youths.
The victim was treated at the scene by paramedics but was pronounced dead a short while later.
Three teenagers have been arrested on suspicion of murder, police said.
Police said that officers and London Ambulance Service were “confronted by a large number of youths” when they attended the scene.
A bus driver aged in his fifties was treated for a head injury at the scene. There are no other reports of injuries.
Detective sergeant Gurj Singh said: “Response officers who attended the initial calls were confronted with up to 100 youths leaving a birthday party gathering at a community centre.
“There appeared to be fighting and tragically a teenager has been found with fatal injuries.”
Local MP Andrew Rosindell said after visiting the area that it was “devastating” that a young life had “so tragically been cut short on our streets tonight”.
Police are appealing for witnesses to come forward, as well as any video footage or images of the violent aftermath to the party.
London has been rocked by a spike of stabbings and shootings, with more than 60 murder investigations launched by the Metropolitan Police so far this year.
Official figures released in April shows there has been a 22% increase in knife crime and 11% rise in gun crime in the past year.