BOSTON -- Boston police are searching for a man they think may be a serial bank robber who's pulled off a number of heists in the city in recent months.

NewsCenter 5's Gail Huff reported that the most recent robbery occurred Tuesday at the Mercantile Bank on Washington Street in the South End.

It was the fourth robbery in the city recently. The other robberies occurred at two Citizens Banks on Boylston Street and Commonwealth Avenue and a robbery at a Sovereign Bank on Beacon Street. The first took place Feb. 25 and the most recent on March 25.

The man's face was caught on surveillance cameras. Police said in most cases the robber hands tellers a note demanding money. He says he has a gun. After getting the cash, in at least two cases he fled in a blue sedan.

Anyone with information is asked to contact Boston police.