An investigation has been launched after a man allegedly "exposed and touched himself inappropriately" in Ashton-on-Ribble, say police.
Police were called shortly after 6am on August 20 to reports that a man had followed two young women along Fylde Road.
He is then said to have exposed himself in front of the young women before making off when one of the pair phoned the police.
A police spokesman said: "We can confirm that we were called to reports that a man had been seen exposing himself and then touching himself inappropriately."
A post warning other women in Preston about the incident was shared over two-and-a-half thousand times on Facebook.
It said: "Please warn other girls in Preston about this guy, he's just followed me and my friend home from town, tried to [perform a sex act] over us and then ran off when I phoned the police.
"Girls this is at 6am when it's light whilst I'm with my friend, it is not safe to walk home on your own."
Police say their enquiries are on-going.