Detectives in Birmingham have told of the "agonising wait" faced by young women stabbed with hypodermic needles in a series of attacks in the city.
Police have released an image of a suspect after a 30-year-old woman was stabbed in the thigh in Broad Street, central Birmingham, at 03:00 GMT on 3 November.
Detectives believe the attack could be linked to two similar incidents in the same area of the city earlier this year, but have said the motive was "unclear."
In the latest incident a woman was stabbed in the thigh and reported feeling a sharp pain, which was later confirmed to be a puncture wound.
On June 23 a 20-year-old woman was stabbed twice in the thigh and buttock while on a night-out and on October 6 a similar attack took place on a 28-year-old woman. Police said they had received five similiar reports in total over the last year-and-a-half.
Detective Inspector Julie Woods said: "Although the women have not been left with any obvious physical injuries they have had to endure an agonising wait to check that they have not suffered any long-lasting health effects.
"Due to the nature of the offences, victims have not realised they have been injured until hours or days later, which has resulted in limited lines of inquiry.
"But we now have a particularly clear image of a man we want to identify in connection with the attacks and I would appeal for him, or anyone who knows who he may be, to come forward."
"These are strange offences and the motive at this stage is unclear, which is why it's so important for us to identify the person in this CCTV image as soon as possible."
Birmingham Police said they had increased patrols in the Broad Street area and the wider city and urged anyone who notices anything unusual to contact police.
Superintendent Danny Long said: "We have increased the number of officers on patrol in Broad Street and around the city centre, particularly since the attack earlier this month, and are working closely with street wardens, street pastors, licensees, door staff and clubbers themselves to keep people safe."
"Birmingham remains one of the safest cities in the UK in which to enjoy a night out but if anyone sees any suspicious activity, I would encourage them to report it to police immediately."
Anyone who recognises the suspect can call police on 101 or Crimestoppers anonymously on 0800 555 111.Reuse content