Detectives investigating the murder of teenager Hani Abou El Kheir in central London, have arrested a further eight people.
Scotland Yard said four men are being held on suspicion of murder and one man and three women on suspicion of assisting an offender. They are in custody at various police stations.
Hani, 16, was found stabbed to death in Pimlico after an attack by a group of people believed to have been wielding knives and swords.
Last Sunday at 6.50pm, officers were called to reports of a youth stabbed near Lupus Street.
When they arrived, they found Hani who was taken to King's College Hospital but later died.
A post-mortem examination found he died from multiple stab wounds.
The latest arrests bring the total number arrested to nine.
On Thursday a 20-year-old man was arrested in north London on suspicion of murder and bailed until late March.
Police believe that at least 10 youths were involved in the incident and are keeping an open mind on the motive.
They will return to the scene of Hani's murder later today and appeal directly to the community of Churchill Gardens Estate, where the youngster lived, to come forward and help with their investigation.
Leaflets will be handed out to residents over the next few days, including an appeal from Hani's mother, Pauline Hickey, with whom he had an "unconditional and unbreakable bond", and ones from other members of his family and his girlfriend.
Det Chief Insp Neil Attewell of the Met's Homicide and Serious Crime Command said: "The tragic events of last Sunday have left Hani's mother and wider family completely devastated.
"I am directly appealing to the parents and carers of those believed to be involved - if you have the slightest indication that your child may have been involved in this incident I encourage you to get them to hand themselves into the police."
Any witnesses or anyone with any information should contact the incident room on 0208 345 3715. if you wish to remain anonymous call Crimestoppers on 0800 555 111.