A fourth teenager has been arrested on suspicion of the murder of a boy at a chicken shop in central London.
Josiph Beker, 17, was stabbed to death outside Edgware Road KFC, Westminster, at about 14:00 BST on 10 September.
A 16-year-old boy was arrested on Sunday in connection with the murder. He remains in custody.
Two 16-year-old boys were charged with murder on Saturday. An 18-year-old arrested over the murder has been bailed pending further inquiries.
Three people have been arrested on suspicion of attempted murder after a 15-year-old boy was stabbed.
The victim remains in a critical condition in hospital following the attack in Tottenham, north London, on Friday.
He was found with multiple stab wounds on Willan Road, in the Broadwater Farm estate, at around 11:15 BST.
Scotland Yard said three males were detained in connection with the incident on Friday evening.
Officers believe the boy was involved in an altercation shortly before he was stabbed, possibly by a suspect riding a bicycle.
Police would like to speak to members of the public who gave first aid to the victim at the scene.
Det Insp Paul Ridley said: “I am keen to hear from anyone who either witnessed, or has information concerning this attack.
“The victim, not yet 16 years old, sustained multiple stab wounds and is fighting for his life.
“If you know anything about the circumstances surrounding the incident or if you witnessed it, please do come forward.
“I would also appeal to the members of the public who valiantly administered crucial first aid to the victim to come forward to my investigation team.”
Anyone with information is asked to contact police on 101.