A 45-year-old woman was sexually assaulted in Dereham's central Market Place in the middle of a week-day afternoon.
It happened last Wednesday at about 2.40pm, close to Poundland in the town centre.
Police said the woman was approached by a man who touched her inappropriately.
A 33-year-old man was arrested in connection with the assault and has been released on bail until June 14 pending further inquiries.
Norfolk Police would like to hear from anyone with information about the incident.
Contact Det Con Peter Sayer at Dereham police station on 0845 456 4567 or call Crimestoppers anonymously on 0800 555 111.
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