An investigation has been launched after a 40-year-old man suffered a serious facial injury during an attack at a flat in Heacham at the weekend.
Police say a group of three men entered the property on Station Road, which was unlocked, between 12.50am and 1.05am on Sunday.
The victim was punched several times by one of the group, who all had their faces covered.
Meanwhile, another member of the gang is said to have picked up a knife from the kitchen table and made threats.
Although the knife was not used, and nothing was stolen before the group left the property, a Norfolk Police spokesman said the man was believed to have suffered a broken eye socket in the attack.
Anyone who saw or heard anything suspicious in the area around the times stated, or who has information about the incident, is asked to contact Det Con Emma Cross, of Lynn CID, via the non-emergency 101 number.