Police are asking for the public's help in catching a man they said choked and sexually assaulted a woman at knifepoint early Tuesday morning in Center City.

The man, captured in surveillance video from two ATMs near the crime scene, is described as a black man, in his late 30s to late 40s, about 5 feet 10, 180 pounds, with short dark black hair and a scruffy face. He was wearing dark blue jeans, a blue or black sweatshirt and sneakers, according to Special Victims Unit Capt. John Darby.

The incident began about 3 a.m., when the assailant persuaded the 24-year-old victim, who was looking for her roommate, to walk with him from 15th and Locust streets to 15th and Vine under the guise that he knew where her roommate was, Darby said.

Then, Darby said, "He produces a knife, he chokes her, robs her of a small amount of currency and some other items including a debit card, and while there he indecently assaults this woman."

After assaulting her, he used her ATM card to try to withdraw money from two ATMs in Center City, Darby said.

Anyone with information on the attacker's identity or whereabouts is asked to call the Special Victims Unit at 215-685-3251.