The victim, a 20-year-old Christchurch man, was approached by three unknown men who threatened him with a knife before demanding he hand over his mobile phone and wallet.
Luckily he escaped without being injured.
Detective Constable Siobhan Lovering, of Bournemouth and Poole CID, said: “This was a cowardly attack on a man in a popular part of Bournemouth.
“I am now able to release an e-fit image of one of the men responsible I would like to speak with as I believe he can assist with our investigation. I urge him to speak with the police and ask if anyone recognises him to come forward.
“I am also keen to speak to anyone who may have witnessed this attack take place or noticed any suspicious activity in the area either prior to the incident or after.
“The main offender is described as an Arabic looking man, well built, aged in his thirties, around six feet two inches tall with a receding hairline.
“He had stubble and a scar on his cheek, and was wearing a black jacket, grey hoodie, Nike trainers and dark jeans.”
Witnesses and anyone with information should call Dorset Police in confidence on 101 quoting incident number 12:130. Alternatively, call the free and anonymous Crimestoppers line on 0800 555 111 where mobile phone tariffs may apply.