A man has been arrested on suspicion of murder after he was seen running away from the scene of an "unexplained" death in Harrow.

The victim, a man in his mid-40s, was pronounced dead on Wednesday afternoon after he was found with an injury inHarrow that was first thought to be a stab or slash wound.

Scotland Yard said they arrested a male nearby on suspicion of murder after officers were told he had been seen running from the scene in Northolt Road in possession of a machete.

He remains in custody at a north London police station as detectives investigate whether the weapon was used.

The Metropolitan Police stressed it had not launched a murder investigation, but instead was treating the death as "unexplained".

A post-mortem examination will confirm whether the wounds were recent or pre-existing, the force said.

Officers remain on the scene and will be trawling through CCTV footage to find out what happened.

Harrow West MP Gareth Thomas said on Twitter: "I am very concerned to hear reports of a recent fatal attack in South Harrow in my constituency."

Mr Thomas said he was in contact with police and the local council, adding: "My thoughts are with the victim and their family."

London's Air Ambulance was called just before 3.15pm. The victim was treated for his injury, but was pronounced dead at the scene at 3.50pm.

"Sadly, despite the efforts of medics, a person died at the scene," a London Ambulance Service spokesman said.

Police said the victim has not been formally identified and his next of kin are yet to be informed.

A 15-year-old girl suffered superficial cuts and a boy, also aged 15, sustained stab injuries after they were attacked by a group in a park in Harrow on Wednesday night in an unconnected incident, police said.

They were both taken to hospital, where their conditions are said to be not life-threatening, after being assaulted in Harrow Recreation Ground.

Officers, who were called at around 9.20pm, are investigating and no arrests have been made.