The suspect was arrested Tuesday after he was identified by victims of the attacks, which took place during the day and early evening from last Wednesday through Saturday, police said. His name was not released because he says he is 16, although police say they doubt that.

The young man appears to be older than 16, and when he was arrested he indicated to police that he was 21 or 22, said Inspector Yvonne Pratt of the sex crimes detail.

"We can't prove it - but for now, he says he is 16, so he is being treated as a juvenile," Pratt said.

The suspect was arrested after he exposed himself to an undercover officer in the park Tuesday morning, police said. He was taken into custody after he boarded a Muni bus on Stanyan Street at 9 a.m.

Police said that in each of the incidents last week, the assailant approached women as they were jogging or riding on park paths and initially asked innocuous questions, such as the time of day or how to get somewhere.

Then he "grabbed them and groped or sexually assaulted them," Pratt said.

He faces several felony counts, including sexual battery.

Police said they brought together a task force late last week and early this week, after the first case came to their attention Friday.

Investigators say there may be other victims who did not report attacks. They encourage anyone with information to call the sex crimes detail at (415) 553-1361.

E-mail Jaxon Van Derbeken at jvanderbeken@sfchronicle.com.

This article appeared on page B - 3 of the San Francisco Chronicle