Six people have been arrested over Rizwan's death

Rizwan Darbar, 17, was stabbed in West Ham Park, Plaistow, east London, on 7 October when he tried to stop a gang stealing a friend's phone.

Police said two youths, 15 and 16, and a man, 20, were held in east London in the early hours of Thursday.

Three 17-year-olds arrested earlier this week have been released on bail until next month.