A teenage boy has been critically wounded and two others injured in three unrelated stabbings across London.
The 17-year-old was found stabbed in Coles Crescent, Harrow, after police were alerted at 20:11 BST.
Two other men, both aged in their 20s, were injured in separate stabbings in Northolt, west London, and Brixton, south London.
Both are in a stable condition, the Metropolitan Police said.
Detectives said a male was arrested near the scene of the stabbing of the 20-year-old in Northolt.
Police said they were called just after 19:00 to reports of a stabbing in Wilsmere Drive, Northolt, and found the 20-year-old suffering stab injuries.
The person arrested, whose age is not yet known, was in custody at a west London police station, the Met added.
The third victim was found injured when police were called at about 18:20 to Southwell Road in Lambeth, south London.
No arrests have been made in either inquiry.
The Mayor of London, Sadiq Khan, said he was due to meet Home Secretary Sajid Javid on Monday to "discuss how we address the scourge of serious violence across Britain" following a fatal stabbing in north London on Saturday.
The killing near Turnpike Lane Tube station in Haringey is the Met's 74th murder investigation this year.