A 14-year-old boy was knocked off his moped by attackers then stabbed multiple times in a targeted attack in east London, Scotland Yard said.

Officers found the teenager with stab wounds after they arrived at the scene in Leyton, in Waltham Forest.

“It is believed that three males got out of the car and then stabbed the victim before returning to the vehicle and driving off,” a spokesman added. “Despite efforts of paramedics, he was declared dead.”

No one has been arrested.

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.”

Forensic investigators at the scene in Leyton, Waltham Forest in north-east London where a 14-year-old boy died after he was found with stab injuries (Yui Mok/PA)

Chief superintendent Richard Tucker said the age of the victim “beggars belief” and a section 60 order was put in place to allow officers to search anyone in the vicinity of the scene for weapons.

In 2018, around a fifth (17 per cent) of homicide victims in London were teenagers, most of whom were stabbed. The youngest were 15.

Detective chief inspector Larry Smith, from the Metropolitan Police murder squad, said: “Everything that we have learned about this attack so far indicates it was targeted and intent on lethal force from the outset.

“We are doing everything we can to catch those who carried out this cowardly attack and bring them to justice.”

Forensic officers assess and comb the area for evidence (Yui Mok/PA)

Investigators are trying to trace the black Mercedes B Class involved in the crash, which is believed to have extensive damage to the front.

Residents who live nearby 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.

Met Police say teenager found with stab wounds was riding moped before collision with car (Yui Mok/PA) (PA)

Anthony Anderson, a mechanic who works near the scene, described the victim as “a very nice guy” whom he had tried to persuade to go to school and stay off the street.

Mr Anderson said he would often give the victim “fatherly advice” and thought he was older than 14 because he had a mature attitude.

He last saw the teenager, who would sometimes come to get his bike fixed, walking down the alley last week.

“He’s somebody I really spoke to a lot, tried to get him off the street, tried to just get him to go to school ... it really, really hit me when I heard last night.”

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Mayor of London Sadiq Khan tweeted to say 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.

Cabinet Office minister David Lidington told the BBC’s Today programme: ”Anybody and particularly any parent’s heart goes out to the family of that young lad – nobody should have to live through their children being attacked, being murdered in this way.

“We need to make sure we have the right law in place to deter stabbings, and the unlawful carrying of knives. The law has been strengthened but critically we have to really step up efforts to wean young people away from getting sucked into these gang networks in the first place.”