Updated 7/30/2012 at 9:51 p.m.

CHICAGO (CBS) — Women in the Humboldt Park and Logan Square neighborhoods are on alert after a pair of attempted sexual assaults.

Police say the same suspect tried to sexually assault two women at knifepoint.

A third attack happened about 1:30 a.m. in Wicker Park.

He is described as African-American and between the ages of 20 and 28, with a medium complexion and dreadlocks. He stands between 6 feet and 6 feet 3 inches tall and weighs 170 to 180 pounds, with a tattoo or a scar possibly below his right eye.

Police released a composite sketch on Sunday evening.

Police say the man approached a woman as she entered her home in the 1700 block of North Humboldt Boulevard around 1:30 a.m. July 11. He first demanded money at knifepoint, then forced the woman into the entryway and attempted to sexually assault her but she called out for help and the man took off.

The second attack happened 25 minutes later in the 1900 block of North Drake Avenue, when the man allegedly forced his way inside a home and attempted to sexually assault a woman at knifepoint in her kitchen.

The victim in that attack the suspect gained access to her residence because she left the door unlocked. The man appeared in her kitchen.

“He pulled out a knife with his right hand and he was like ‘Get on the bed. If you scream, I’m going to kill you,’” the woman told CBS 2’s Pam Jones.

“Then he reached up and he choked me,” she says. “Then he let go for whatever reason. I was still in adrenaline mode and I actually tried to run out my back door, and I slipped and fell.”

She says she remembers his face and the teardrop-shaped tattoo under his right eye.

“I’m just glad nothing worse happened.”

In each incident, the suspect zeroes in on a woman who’s by herself.

“He is bold with these women, but he’s targeting them in the late hours of the evening and probably because they are alone,” Chicago Police Sgt. Mia Ogliore said.

Police say the man may have been riding a bike.

Anyone with information is asked to call Area North police detectives, at (312) 744-8261.