A 14-year-old boy has died after he was stabbed by attackers who are believed to have knocked him off his moped, Scotland Yard has said.

Officers were called to Bickley Road, Leyton, in Waltham Forest, shortly before 6.30pm on Tuesday to reports of a road traffic collision.

The Metropolitan Police said the teenager was found with stab wounds, and detectives have established he was riding a moped that had been involved in a collision with a car.

A spokesman for the force said: “It is believed that three males got out of the car and then stabbed the victim before returning to the vehicle and driving off.

“Despite efforts of paramedics, he was declared dead at 7.09pm. Next of kin have been informed.

“A crime scene is in place. The Homicide and Major Crime team has been informed. There has been no arrest. Inquiries continue.”

One man who did not want to be named described how a witness of the incident came into the premises where he works nearby, clearly horrified by what they had seen.

He said the witness told him how the teenager who was on the moped was struck by the car which was travelling in the opposite direction.

“They said they knocked him off the moped and four people got out of the car and they stabbed him seven times – there were unsurvivable wounds in his back,” he said.

He said the witness recalled how the boy was possibly unconscious when he was stabbed, with his helmet thrown up to 10 metres away.

The man added: “He thought it was an accident, that somebody had knocked someone, but then he said they quickly came (out of the car).

“They beat him up, and they stabbed him, and they left.”

Residents who live on Bickley Road said they did not hear any shouting or screaming.

They said it was not until they saw the blue flashing lights from the emergency services that they knew something had happened.

At about 11pm on Tuesday the street remained cordoned off at both ends and a forensic tent had been erected in the middle.

Forensic officers in blue suits could be seen assessing and combing the area for evidence.

Mayor of London Sadiq Khan tweeted to say that he was “greatly saddened” by the news of the fatal stabbing.

“My thoughts are with his family and friends. If anyone has information about this horrific incident – please contact the Met Police on 101 or Crimestoppers anonymously,” he added.