CHICAGO (CBS)–Chicago police issued a community alert Friday warning North Side residents about a string of robberies reported between Jan. 5 and 29 in the Streeterville and River North neighborhoods.

All the robberies follow the same pattern. A group of two to four men approach a person on a cell phone and forcibly grab it from their hands, according to police.

After two of the robberies, the suspects fled in a black four-door sedan, police said.

The robberies occurred on the following dates and locations: 

500 North Rush Street, in the River North neighborhood, on Jan. 5

100 block of East Huron Street, in Streeterville, on Jan. 9

300 block of East Illinois, in Streeterville, on Jan. 9 and 10

600 block of North Wells Street, in River North, on Jan. 21

100 block of East Ohio Street, in River North, on Jan. 28

The suspects are all black males between the ages of 15 and 21, police said.

Anyone with information is asked to call Area Central Detectives at 312-747-8380.

Police offered the following tips if you become a victim:

-Remain Calm

-Remember any unique physical characteristics on the assailant(s).

-Call 911 immediately