Chicago police are asking northwest side businesses owners to make sure surveillance cameras are turned on after several robberies in the Jefferson Park and Portage Park neighborhoods.

A man is suspected in at least four robberies.

Police say he approaches a cashier displaying a knife and then takes off with the cash.

Last week, there were robberies on and near the 5300 block of North Milwaukee Ave.

Two other robberies occurred  nearby.

But an attempted robbery at an LA Tan salon was foiled by a brave cashier.

Three other people in the home were able to get out safety.

The robber is described as white, about 20-30 years old, 5 feet 7 inches to 5 feet 10 inches tall, weighing 170-180 pound.

He was wearing a black jacket or black hooded sweatshirt, blue jeans and gym shoes.