A teenager has been arrested on suspicion of murder after police were called to reports of a collision involving three vehicles and a fight which took place afterwards.

Officers found the victim, in his 20s, with stab wounds in Gammons Lane, Watford, just before 3am on Saturday.

He was taken to hospital where he was pronounced dead.

Police were also called to reports of another man who was found with a stab wound to his arm in nearby St Georges Road.

The man was also taken to hospital for treatment.

Police believe the two incidents are connected.

Watford Chief Inspector Matt Phillips said: "I understand this sad news will cause alarm to the local community and I would like to reassure Watford residents that we are working closely with MP Richard Harrington and Watford Borough Council to support anyone who has been affected by this terrible loss of life."

Detective Chief Inspector Justine Jenkins, from the Bedfordshire, Cambridgeshire, and Hertfordshire Major Crime Unit, said a 19-year-old man from Watford has been arrested on suspicion of murder.

She added: "We are still in the very early stages of our investigation and extensive enquiries are being carried out to help establish the sequence of events.

"I would urge any witnesses or anyone with information to get in touch straight away.

"In particular, I would like to hear from anyone who believes they might have dash cam footage of any of the vehicles in Watford overnight on Friday 30 August into this morning."

The cars believed to be involved in the collision are a grey Volkswagen Golf, a blue Vauxhall Corsa and a black Vauxhall Astra, police said.