A 20-year-old woman got off a bus on Anlaby Road and began to walk towards Park Street when she was approached by a young man asking her for a cigarette. The woman declined to give the man anything despite his being verbally aggressive.
The woman carried on walking, and the man appeared to walk away.
However, a short time after, at the junction of Park Street and Anlaby Road, the woman was then approached from behind and was struck on the back of the head by a hard object.
As the woman got to her feet, she saw the man who had previously approached her with two other male associates.
All three men then made off on foot. The woman did not sustain injuries, which required hospital treatment.
The Trespass camouflage wallet contained a bank card, personal documentation and a door key.
The first man is described as being white, of medium build, approximately 5ft 10ins aged between 15 and 20 with short dark-brown hair. He was clean-shaven and wearing a dark-brown Umbro tracksuit with a white stripe on each arm.
The two other men are both described as white, aged between 15 and 20 and approximately 5ft 7ins tall. One of the men was of slim build, had short mousey coloured hair, was clean-shaven and said to be wearing a dark leather jacket with pockets and a material hood, with dark-blue jeans.
The other man was said to be of medium build, with short brown hair and wearing a light-blue t-shirt and dark-blue jeans.
Anyone who may recognize the men from the description or has any information in connection with the incident is asked to contact Humberside Police on the non emergency number 101 quoting crime reference number 1916833 or Crimestoppers anonymously on 0800 555 111.