Police say the attack happened near the bus station in Raven Meadows, at around 6.40pm on Saturday.
The victim, a man in his 30s, was approached by three men who proceeded to assault him on the Smithfield Road side of the station.
He was left unconscious, and following the incident the victim discovered that cash and tobacco had been taken.
Police say the suspects were described as white men in their 40s. Officers are continuing to examine CCTV footage.
A spokesperson from West Mercia said: "We are appealing to anyone who was in the area at the time that may have witnessed the robbery or saw the suspects either before or afterwards.
"We would also like to hear from any motorists who were travelling through Raven Meadows and Smithfield Road area at the time and may have dash-cam footage which has picked up the offenders."
Anyone with information or footage is asked to contact PC Jake Garratt at email@example.com or 07929 721818 quoting incident number 142i of March 19.