Police said it happened near West Berteau and North Central avenues in Portage Park around 8:30 a.m.
A 13-year-old girl was walking southeast through the park when she saw a man with a gray or black dog walking northeast, police said.
Police said the man tried to lure the teen after getting her attention. She quickly went to a nearby building, where she alerted park officials.
The suspect fled in an unknown direction. He is described as 50-60 years old and about 5-foot-8 with a gray goatee. He wore a tan/brown large t-shirt and tan/brown long shorts.
Area Five detectives asked anyone with information to call them at 312-746-6554 or submit an anonymous tip at CPDTIP.com and use reference # JK314535.
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