A 32-year-old man sustained a suspected broken arm after he was assaulted in the Strand Road area of Derry on Friday evening.
At about 9.15pm, the man answered knock at the door of a flat and was confronted by two men and a woman. He sustained the arm injury when struck with a plank of wood.
Information can be given on the police non-emergency number 101. Alternatively, it can be provided to the Crimestoppers charity anonymously on 0800 555 111.