The girl was walking home on her own about 3.30pm when the man pounced.
She had no warning and did not suspect she was being followed.
The man grabbed her by the arm and she immediately began to fight back.
At one stage the man struck the girl on the face.
"She managed to break his grip and get away," Mr Smith said.
The distraught girl ran to her home, which was only a short distance away.
Her mother took her to a medical centre for treatment to minor abrasions she suffered in her struggle to get away.
She told police she saw something shiny in the man's pocket but wasn't sure what it was.
"This was a very serious incident and we are appealing to the public for any information," Mr Smith said.
The offender was described as a Maori or Pacific Islander in his early 30s, about 1.82m tall, with facial hair around the jawline.
He was wearing blue jeans, and a jacket over a black hooded sweatshirt with a beanie underneath.
Detectives made door-to-door inquiries to see if there had been any sightings of the man.
There had been no other incidents of that kind in the immediate area, Mr Smith said, but there had been similar incidents in Napier and Hastings over the past year.
The most recent occurred last month when a European man in his 40s approached a 16-year-old Napier Girls' High School student who was on her way to school.
- APN