Detectives are investigating an assault on a man and woman at Northland Road at 12.15am on Saturday, December 12.
Three men entered the flat and a firearm and knife were used. The man was struck on the face with the gun, which was recovered in follow up searches.
The culprits demanded money from one of the victims.
They made their escape with two mobile phones, cash and a holdall containing Christmas presents.
One man was arrested and is currently assisting police enquiries.
Police are appealing for witnesses in the area of Northland Road who may have seen or heard suspicious activity. The number to call is 101, or Crimestoppers on 0800 555 111.