Police have increased patrols on walking trails surrounding a lagoon in Sydney's northern beaches after multiple women reported being "sexually touched" allegedly by a man on an e-bike.
The incidents, which number six to date, took place between October 1 and October 12 in broad daylight while the women were walking or running at Narabeen Lagoon and in the surrounding bushland.
The incidents took place between October 1 and October 12 in broad daylight. (ABC News)
In an update on Saturday afternoon, Superintendent John Duncan said it was alarming that women were being harassed.
"We take these matters very, very seriously," he said.
"In consultation with State Crime Command and the Sex Crime Squad, we've got a number of overt and covert activities.
"We have a number of our uniformed and plain-clothed officers in the area."
Most of the alleged offending occurred between 4pm and 6pm.
In some cases several incidents occurred on one day, which according to police "tends to suggest it's probably someone who is local and someone nearby".
Police say the man is believed to be aged under 25 years and of Caucasian appearance. (Supplied: NSW Police)
Earlier, police released an image of a man they would like to speak to.
He is riding an e-bike and is described as "being of Caucasian appearance, believed to be aged under 25 years, about 175cm tall and of medium build".
Police believe just one person is involved, but are "keeping their options open".
"I'd imagine that person, or their families or friends, will actually know who that is,"
Superintendent Duncan said.
"And we encourage them to come forward and help with our investigations."
'Rode away on an e-bike'
The first reported incidents happened on October 7 and October 8.
"In each incident, a male allegedly approached women on walking trails, sexually touched them and then rode away on an e-bike," police said in a statement.
"In one of the incidents, the man also made inappropriate sexual comments."
The first incidents reported to police took place on walking trails near the lagoon. (ABC News)
After a public appeal for information on October 12, police received an additional three reports — one dating back to the first of that month.
The woman alleged she was approached by a man near South Creek Road at Wheeler Heights about 4.30pm and allegedly sexually touched before he rode away on an e-bike.
On October 12, in two separate incidents between 5pm and 5:30pm, two women reported being sexually touched by a male riding an e-bike.
There have been no reports since then, Superintendent Duncan said, but he feared there may be more cases.
"We do believe that there are probably more victims out there that may have some information or may have been a victim of this particular crime," he said.
"And we'd like them to come forward and contact either Crime Stoppers on 1800 333 000 or Dee Why Police Station."
Anyone with dashcam footage is also urged to contact police.