The victim was walking along Cross Street, in St Leonards, when a member of the group put a lit cigarette in his hood. He realised his jumper was burning after smelling smoke and managed to pull it off before he was burned.
Shortly after he was approached at a bus stop on London Road and surrounded by the group, one of who threatened him and demanded he hand over his phone. He was punched in the stomach when he attempted to get away.
Police say the incident took place at around 5.15pm on Thursday February 23.
Detective Constable Rhys Bendon: “Putting a lit cigarette into someone’s hood is incredibly dangerous. The victim was shaken by the robbery, but thankfully suffered only slight injuries from being punched.
“There were a number of people at the bus stop and on the bus at the time of the assault who may have information that could help the investigation. I would urge anyone who witnessed what happened to contact police.”
Police arrested a 16-year-old boy from Hastings on suspicion of robbery and possessing a bladed or pointed article. He has been released on bail pending further enquiries until 14 April.
Police also arrested four local boys, aged 13, 15, and two age 14, on suspicion or robbery. They were later released without further action.
A shop gift voucher was stolen during the robbery.
Anyone with information is asked to contact Sussex Police on 101 quoting serial 1266 of 23/02 or anonymously to the independent charity Crimestoppers on 0800 555 111.