Rizwan's family has offered a �10,000 reward to catch his killers

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

Two 17-year-old youths were arrested on Tuesday and a third youth, also 17, was arrested on Wednesday.

All three were bailed until next month while enquiries continue.

Rizwan was the 20th teenager to have died as a result of a knife or gun-related crime in London this year.