The 11 year old victim was in Lower Road Recreation Ground just before 4pm when he was approached by the group of older boys.
They accused him of filming them before grabbing his phone and smashing it, then running off towards Grange Community Centre.
The 12, 14, 15 and 16 year old boys were all arrested on suspicion of robbery.
Any witnesses of anyone with information on the incident is urged to contact police on 101.