Police investigating a report of an assault outside Tesco in Lewes are appealing for witnesses to come forwards.
Officers were called to Brooks Road shortly before 9pm on Friday (7 May) after a 16-year-old boy was assaulted.
He suffered a serious injury requiring hospital treatment.
A 16-year-old boy was arrested on suspicion of causing grievous bodily harm with intent and has been released on bail while enquiries continue.
Two further boys – aged 17 and 15 – were arrested on suspicion of wounding with intent and have also been bailed.
Officers are appealing to anyone who witnessed what happened or may have relevant footage of the incident to come forwards.
Anyone with information can report online or call 101, quoting 1438 of 07/05.