Men impersonating police officers with handheld sirens attempted to pull over two cars in separate incidents Sunday, authorities said.

A woman driving a 1998 black Chevy Cavalier down Phelps Street around 1:45 a.m. noticed a tan Jeep SUV following her. She later heard and saw sirens coming from the Jeep, so she pulled over at the intersection of East Phelps Street and North Waterman Avenue, police said..

A man with a flash light, wearing a white, long-sleeve shirt with blue markings approached her vehicle and identified himself as being with the Prospect Heights Police Department. When the woman asked for a badge and identification, the man went back to his vehicle and left..

On Sunday just before noon, a man driving a black Jeep Grand Cherokee attempted to pull over another driver at East Hintz and North Buffalo Grove roads, police said.

The driver told police that the Jeep, which had either two or three male passengers, passed and then cut in front of the car. Later, the Jeep pulled behind the vehicle and the driver saw a flashing blue strobe light and heard sirens. There also was a yell to pull over.

When the driver did not stop, a glass bottle was thrown from the Jeep and struck the vehicle's tail light, police said.

Arlington Heights police advise anyone who is asked to pull over by a suspicious or unmarked vehicle to call 911 and drive to a well-lit area, such as a gas station or shopping mall, where there may be other people.

Drivers should give the 911 dispatchers their location and where they are heading and ask if any officer is attempting to stop a vehicle in that area, crime prevention officer Doug Hajek said.