CHICAGO (CBS) -- Police are warning residents that a trio of knife-wielding robbers struck six times in less than two hours Monday in the Bucktown, Lincoln Park and Lakeview neighborhoods on the North Side.

In six separate incidents between 3:45 p.m. and 5:01 p.m. Monday, the three suspects approached victims, physically restrained them by grabbing them, placing them in a headlock or surrounding them so there is no escape, showed a knife "in a menacing manner" and then robbed the victims of their cellphones, credit cards or cash, according to a community alert from Chicago Police.

The suspects then ran to a waiting black Nissan or Honda hatchback vehicle, which sped away, police said.

The robberies happened:

• About 3:45 p.m. in the 1900 block of North Wood;
• About 3:58 p.m. in the 2500 block of North Greenview;
• About 4:15 p.m. in the 2700 block of North Mildred;
• About 4:50 p.m. in the 3000 block of North Greenview;
• About 4:50 p.m. in the 3000 block of North Ravenswood; and
• About 5:01 p.m. in the 3700 block of North Greenview.

The three suspects are described as black males, between 13 and 25 years old, police said. One robber was about 5-foot-5 and 150 pounds, while another was about 6 feet, 180 pounds and wearing a white T-shirt.

Anyone with information on the robberies is asked to contact Area North detectives at (312) 744-8263.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2016. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)