Cops in four towns are on the lookout for a serial armed robber who has struck convenience stores and gas stations at least nine times since the beginning of February, police said.

The man, who has been captured multiple times on surveillance cameras, rushed out of an East Boston Mobil station emptyhanded when the clerk behind the counter yelled at him March 7, police said. But three days later, cops said he struck again, this time in Everett, where he showed a weapon and demanded money.

“Luckily, no one has been injured,” said Lynn Police Lt. Chris Kelly. “Even though there have been no injuries as of yet, this is a very dangerous situation to the store employees and potential customers when dealing with an armed robbery involving a handgun.”

The first robbery was February 2 in Lynn and he is suspected of carrying out five additional robberies in that city, police said. On Feb. 24 he struck the Corner Market on Broadway in Chelsea, and Sunday he robbed a 7-Eleven store on Ferry Street in Everett.

Police said the suspect has been described as a middle-aged black man, wearing a gray dark colored jacket, dark jeans and dark sunglasses.

Kelly said police have been working with store owners on ways to prevent armed robberies.

“We also have a city ordinance requiring surveillance equipment and we give them tips on what to look for and preventive steps such as keeping the windows clear from unnecessary signage and having two employees working at all times,” he said.

Anyone with information is asked to call Lynn Police at (781) 595-2000 or the East Boston police district at (617) 343-4220. Anonymous tipsters can call (800) 494-TIPS or text the word TIP to CRIME (27463).