A man in his 20s has died after being stabbed in a fight near Ealing Common, west London.
Officers from the Metropolitan Police were called to reports of a fight close shortly after 18:00 BST and discovered the man suffering from stab injuries.
Members of the London Ambulance Service and the air ambulance also attended, however the man was pronounced dead at the scene at 18:48.
His next of kin have been informed and a post-mortem will be held.
A man was arrested on suspicion of affray and was taken to a west London police station where he remains in custody.
Inquiries are ongoing.
Anyone with information is asked to call officers on 101.
A section 60 order is now in place for the Hillingdon and Ealing areas until 07:00 on Wednesday, allowing the police greater search powers for a limited period.
This order comes after a murder investigation was launched when a man was stabbed to death on a train at Hillingdon station shortly before 16:00 on Tuesday.
A man was stabbed to death in a south-west London street by the person he had been walking with, police have said.
Tesfa Campbell, 40, was found by police responding to reports of a fight on Latchmere Road in Battersea on Wednesday. He died in hospital.
Det Ch Insp Simon Harding, from The Met, said it is believed Mr Campbell was walking on Burns Road with another man who stabbed him and fled on foot.
No arrests have been made in connection with his death.
Police found Mr Campbell injured at about 14:45 BST and have appealed for witnesses who were in the area at the time, “particularly” around the nearby Latchmere Leisure Centre.
Det Ch Insp Harding said: “This stabbing happened in broad daylight and we believe there are people out there who can help us establish the facts of the incident.”
A post-mortem examination of Mr Campbell, who was from Croydon, will happen in due course.