A 16-year-old boy has been chased down and stabbed to death with a "machete" in London.

A witness heard the teenager begging for help before he was murdered, minutes after another stabbing on the other side of the capital.

Police were called to Munster Square in Camden shortly after 11pm on Monday night.

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“Officers and the London Ambulance Service attended and the male was pronounced dead at the scene,” a spokesperson for the Metropolitan Police said. 

“A crime scene remains in place. There have been no arrests and enquiries into the circumstances remain ongoing.”

Detective Chief Inspector Paul Healy said the victim had been "chased around the square by a number of suspects" before being stabbed multiple times. 

“The suspects made off in a vehicle which was discovered burnt out nearby," he added. "Another vehicle believed to be involved in the incident was also found burnt out some distance away.

“We’re still in the early stages of our investigation and we are urging to those who have information to do the right thing and speak to us."

A witness said she saw three men “screaming and laughing” as they pursued the boy with a weapon she described as a machete.

The woman, who did not want to be named, said the victim was banging on a family's front door appealing for help before he was stabbed.

“Through my bedroom window I could see everything," she added. "We just saw the three boys holding him. He said 'help me, help me, help me'. He collapsed on the floor and then it was quiet.”

The victim's stomach was visibly bloodied, she said, adding that the attackers fled in a car.

A first-aid bag could be seen on the pavement outside flats on Tuesday morning, with white sheeting on the ground nearby.

Police are also appealing for information on a stabbing that took place minutes before the Camden attack in Norbiton, south-west London.

Cressida Dick: Stabbings of young people 'tragic and worrying phenomenon'

Officers were called at 11pm on Monday to reports of a fight between five people and an injured person was treated at hospital.

Detectives believe the victim may have been the victim of a robbery. 

More than 80 people have been killed in London so far this year, after homicides hit a 10-year high in 2018.

Metropolitan Police commissioner Cressida Dick has named street violence as her “number one priority” amid rising violent crime across England and Wales.

The London mayor, Sadiq Khan, has given police funding to recruit more officers and set up a violence reduction unit for the capital.

A recent Home Affairs Committee report found youth violence had become a "national emergency", exacerbated by Conservative budget cuts to police and youth services.

Since becoming prime minister, Boris Johnson has promised funding for 20,000 more officers nationwide and relaxed rules on the use of controversial powers to stop and search people without reasonable suspicion.

On Monday, the government announced £35m funding for 18 areas to set up local violence reduction units, which include police, councils, health and social workers.

Kit Malthouse, the policing minister, said: “To beat knife crime we must do two things: first we need assertive, high profile police enforcement and second, we need a coordinated approach to the long term solutions to violence in society, especially amongst the young. These new units should help us get results on both.”

Anyone with information on the Camden stabbing is asked to call police on 101 or Crimestoppers anonymously on 0800 555 111.

Additional reporting by PA