Two armed robbers held a 25-year-old Brighton man at gunpoint in his flat and stole three valuable watches from him.
Sussex Police were called while the robbery was taking place but the gunmen had fled by the time officers arrived at about 2pm on Saturday (3 December).
They cordoned off the flat in Regency Square and the area around it while firearms officers carried out a search.
The victim, who police said was not seriously injured, knew one of the gunmen but details of the man’s identity have not been released.
The suspects were described as black, one in his late twenties to early thirties and the other slightly older.
The older man was described as tall and slim and wearing glasses. The other was described as shorter and of a stocky muscular build.
Both men spoke with London accents.
Detective Sergeant Helen Paine, of Brighton and Hove CID, said: “We are appealing for witnesses and would ask anyone with information to contact Sussex Police immediately.”
Witnesses can contact the force by calling 101 or they can call the independent charity Crimestoppers anonymously on 0800 555111.