A 19-year-old woman was grabbed from behind as she was walking through an alleyway in Banbury on Saturday.
It happened at about 6.10pm between Fiennes Road and Edmunds Road, where she was pulled backwards by a man. She screamed and the man ran off.
The offender was white or light skinned with an average build and short brown hair. He was wearing grey cotton jogging bottoms and a hip-length black or dark navy jacket with a slight sheen to it.
Police are keen to speak to a man walking in the opposite direction down the alleyway towards Mold Crescent, and two teenagers, a man in a white hooded top and a girl in a pink hooded top. They crossed from the direction of Fiennes Road and went through the gate towards Princess Diana Park.
Anyone with information should call investigating officer PC Beth Cocker on 101, or Crimestoppers anonymously on 0800 555111.