CHICAGO (CBS)–Police have issued a community alert about a string of carjackings on Chicago’s North Side.

Four similar incidents occurred in Lakeview, Andersonville, North Center and Lincoln Park between Aug. 27 and 28, police said.

In each incident, two offenders in a car rear-end the vehicle in front of them. When the victim pulls over, they approach and brandish a firearm while demanding the victim’s vehicle.

Police said the offenders were described as two black males wearing ski masks.

The carjackings occurred at the following locations and times:

• 800 block of W. George St., Monday, August 27, 2018 at 12:07 a.m.

• 1700 block of W. Farragut Ave., Monday, August 27, 2018 at 1:20 p.m.

• 2100 block of W. Belle Plaine Ave., Tuesday, August 28, 2018 at 9:30 p.m.

• 2500 block of N. Bosworth Ave., Tuesday, August 28, 2018 at 9:03 p.m.

Anyone with information is asked to call Area North Detectives at 312-744-8263.