The incident took place in a park off Gleadless Road on Sunday, May 1, and left a woman injured.
A South Yorkshire Police spokesperson said: “At about 5.30pm, the victim was riding her electric scooter through the park when it is reported that three men wearing hoodies pushed her to the floor. The three men were then disturbed by a passer-by and ran off.
“When she got home, the woman noticed she had received what looks like a slash wound to her leg which may have been caused by a knife.
“Officers are now appealing for anyone with information, or who may have been in the area at the time and saw or heard anything suspicious to come forward.”
Anyone with information is asked to call police on 101, quoting incident number 684 of May 1.