Detective Ash Clements of the Eastern Bay of Plenty Adult Sexual Assault Team said the incident was of "extreme concern both to the police and the wider community".
"The actions of this male were unprovoked and have occurred in daylight hours on a very public road.
"Members of the public are asked to provide any information, even if it appears to be minor, to police as soon as possible."
Information can be provided to the Whakatane police on (07) 308 5255, the Edgecumbe police on (07) 304 9004, or anonymously via the crime stoppers line 0800 111 555.