A 21-year-old man was pushed to the ground, punched in the face and threatened with a knife by four men on Monday.
Police are now appealing for witnesses to the incident which happened as the victim was walking in the H9 underpass between Wavendon Gate and Brinklow at 2pm.
Four men approached the man, punched him in the face, pushed him to the floor, and threatened him with a knife, before demanding his mobile.
They were then disturbed and made off without taking anything, leaving the victim with injuries to his stomach and face.
The four offenders were all white and thought to be in their 20s. One of them was wearing a black face mask and the other three covered their faces with scarfs and hooded tops. Police want to speak with anyone who saw them in the area. Call 101 if you have any information.