On the same afternoon last week that two MSU students were robbed by a teenager armed with a glass bottle, an 18-year-old man says he was threatened by a thief nearby claiming to have a knife.

MSU police say both incidents took place near bike racks in the Brody Complex at 1:40 p.m. and 3 p.m. on Oct. 20. None of the students accosted were injured, MSU police Sgt. Florene McGlothian-Taylor said.

The attacker - described in both cases as a thin 15- to 17-year-old man, wearing a leather jacket and riding a BMX bike - has not been apprehended.

The 18-year-old victim reported the incident outside Armstrong Hall to police on Friday afternoon, four days after the nearby attack on the other students was reported.

Police say the man who attacked the 18-year-old threatened to cut him with a knife if he didn't give him money. The assailant motioned as if he had a knife, but the victim never saw a weapon, police said.

"He asked him for money, but the complainant didn't have any," McGlothian-Taylor said.

The attack had a similar nature to the one reported later that afternoon by two 19-year-old male students, who say a teenager approached them outside Bryan Hall. The teenager apparently threatened them with an empty glass bottle, demanding money.

He fled the scene with a small amount of cash.

McGlothian-Taylor said police continue to investigate both cases.

She did not want to speculate on whether they are related. But police are warning students to be vigilant in knowing their surroundings.

"We want to make sure students stay alert in the area," she said. "If they see anything suspicious, make sure they call the police department."

It is not clear if the incidents are related to a string of aggressive robberies in East Lansing in recent weeks.

On Thursday night, a man told police he was kicked and punched by a 20- to 30-year-old man on the corner of Spartan and Albert avenues. The attacker stole the man's cell phone and jacket before fleeing.

Police have not made an arrest in connection with that robbery.

Earlier this month, a 24-year-old man was approached at gunpoint while sleeping in his car in an alleyway near the 100 block of Gunson Street. Police arrested a suspect a short time later.

A series of five aggressive robberies in the city in late September has prompted East Lansing police to remind residents to report unusual behavior.

There have been a total of 24 aggressive robberies in the city this year.

No serious injuries have been reported.

Steve Eder can be reached at ederstev@msu.edu.