Sussex Police said the men, who were wearing dark clothing and face coverings, broke into a flat in Sackville Road at around 8.30pm on Monday (May 11).
The front door was damaged and a mobile phone was taken, police said, before the trio left. They are believed to have got into a black vehicle.
Police said this is thought to be an isolated incident and there is not believed to be a wider threat to the public.
If you believe you may have seen the suspects, witnessed the burglary or have information to assist the police investigation please report online or call 101 quoting 1272 of 11/05.