Police are looking for a man suspected in a string of armed robberies in subway stations in downtown Manhattan and Brooklyn this week.

The suspect has targeted teenage boys and men between 15 to 30 years old, telling them he has a gun with a silencer as he forces them to turn over personal property before running away, police say. 

The robber struck late Sunday on East First Street; early Monday at the Second Avenue and East Houston Street subway station; Monday afternoon at the Dekalb Avenue subway station; shortly after midnight Tuesday on the southbound F train as it was approaching the West Fourth Street and Sixth Avenue subway station; and early Tuesday on the southbound D train as it was leaving the DeKalb Avenue subway station.

Riders along the targeted lines said they were surprised to hear about such brazen robberies.

"That does sound very unusual," said one man.

Anyone who recognizes the suspect seen in the surveillance video, taken around the time of the D train robbery, is asked to contact Crime Stoppers at 800-577-TIPS or at nypdcrimestoppers.com.