Police have made two more arrests after Abdullahi Tarabi was knifed to death after being chased through a west London estate.
The 19 year old collapsed in an alleyway after being stabbed in the stomach in broad daylight near his home in Northolt at about 3.30pm on Tuesday.
Witnesses described how the teenager cried for help before been dragged to the safety of a nearby house. Paramedics at the scene battled to save the young man but he was pronounced dead just after 5.30pm.
A post-mortem examination held at Uxbridge Mortuary on Thursday confirmed cause of death as the result of a stab wound to the abdomen.
Three 19-year-old men and an 18-year-old man who were initially arrested on suspicion of attempted murder and later arrested on suspicion of murder have been released on bail while police investigate.
Two further arrests have been made. A 16-year-old boy was arrested in Harrow on Thursday and a 17-year-old boy was arrested on Friday at a north London police station.
They were both arrested on suspicion of murder and are currently in custody at north London police stations, police said.
Anyone who witnessed the incident or has information about the attack is asked to contact the incident room on 020 8358 0300 or via Twitter @MetCC.
Alternatively Crimestoppers can be contacted anonymously on 0800 555 111 or online at the crimestoppers-uk.org website.