Sussex Police are investigating a robbery and an attempted robbery in Brighton last night (April 3) when victims were threatened with a handgun.
Police said the incidents occurred within an hour of each other and detectives are currently treating them as linked.
In both cases the main suspect is described as a white man with facial hair and hair cut short at the sides, 5' 8" - 5' 10", wearing jeans, a baseball cap and a black coat or jacket with a fur hood, and sunglasses.
No one was hurt in either case and no arrests have been made, police said.
Sussex Police said: "The first incident was reported at around 9.20pm in Bartholomew Square, Brighton. Two brothers, aged 18 and 19, and both from the United Arab Emirates, were confronted by the robber who pointed a pistol at them and demanded they hand over their possessions. These included bags, mobile phones, wallets, shoes and clothing.
"On this occasion the suspect, who made racist remarks towards his victims, was accompanied by a black man - tall, in his 20s and wearing a black hooded jacket - and an Asian man in his late 20s wearing a black coat.
"The second incident was an attempted robbery at 10.20pm on the lower promenade near Brighton Pier when the victim was threatened with a handgun but nothing was taken. The suspect, who was alone, closely matched the description of the main offender in the earlier incident."
Detective Sergeant Joe Jardine of Brighton Police, said: "High visibility patrols have been deployed in the area and officers are keen to hear from anyone who may have seen what happened in either case, who noticed anything suspicious or who may have relevant dash-cam or closed circuit television (CCTV) footage."
Anyone with information shoudl contact police online with the reference 47190053298.