Patrolling Met Police officers came across a fight outside Sainsbury’s in Garratt Lane just before 5pm yesterday.
Two teenage boys, both believed to be aged 15, were found suffering from knife injuries.
Another male was found at the scene with a head injury; he did not require hospital treatment.
A 17-year-old has been arrested on suspicion of affray and a 19-year-old on suspicion of causing GBH.