EVANSTON, Ill. (CBS) — Northwestern University students are on alert, after someone punched a student and robbed him of his smartphone on campus.

Around 11:30 p.m. Saturday, a male Northwestern student was walking south on Sheridan Road near University Place, when a suspect approached him from behind and asked him what time it was, a Northwestern police alert said.

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The student pulled out his smartphone, told him the time, and kept walking. He turned west on University Place, and as he was walking between the 600 and 700 blocks of University Place, the suspect again approached him from behind, grabbed him and demanded his smartphone, the alert said.

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The suspect — who said he had a knife but did not show one — punched the student in the face, snatched the phone from his hands and pushed him down, the alert said.

The suspect fled west on University Place and then south on Sherman Avenue. The victim chased after the robber but lost him as he approached the downtown Evanston area, the alert said.

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The victim contacted the Evanston Police and their officers responded with the Northwestern Police Department.

Police searched for the suspect — described as black and between the ages of 18 and 22, about 6-foot-1 to 6-fot-2 — but he was not found. The suspect weighs about 180 pounds, has an average build and was wearing a multi-colored hat with stripes and blue jeans during the robbery, according to the alert.

The victim declined medical treatment.

Anyone with information should contact the Evanston Police, (847) 866-5000.

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The Sun-Times Media Wire contributed to this report.