Boston and MBTA Police are stepping up patrols this week and warning the public after a flurry of street robberies targeting women that may be the work of a single, armed bandit. The incidents have all targeted women who were walking home from Red Line stations, including JFK-UMass, Savin Hill, Shawmut and Ashmont.

“We’re concerned about it,” said Captain Richard Sexton, commander of the Area C-11 police district. “It seems like it’s one person right now. We’ve had a few others on the district recently, but there’s definitely a pattern going here along the Red Line.”

Sexton said that the robber has accosted people between the hours of 7 p.m. and 10:30 p.m. In a few instances, the suspect — described as a black male with a thin build, age 20-30, wearing a grey hooded sweatshirt— flashed a handgun.

Another common denominator in each incident, Sexton said, is that the robber attempted to engaged the victims— all of them female— in a brief conversation before demanding money.

The most recent incident took place Tuesday night on Beaumont Street near Ashmont station. On Monday, a woman was robbed at gunpoint on Kenwood Street in the vicinity of Shawmut station. Two earlier incidents that may be the work of the same suspect were reported in Savin Hill between Nov. 30 and Dec. 1 on Carson Street and Maryland Street respectively. In both instances, the victims were accosted near their homes and escaped inside without injury or losing property.

“The incidents on Carson St. and Maryland St. have similarities that may indicate the same suspect is involved based on physical descriptions and asking victims 'where is the train station’,” Captain Sexton said. “In this week’s incidents near Ashmont and Shawmut, the victims also stated that the suspect seemed to be approaching them with questions as he approached them."

Among the other incidents reported on C-11 in the last week, Capt. Sexton said a 14 year-old boy was assaulted and robbed by two suspects on Crescent St./Sydney Street at 6:30 a.m. on Nov. 29; and a pizza delivery driver was accosted at knifepoint by two men in a blue GMC Yukon on Grampian Way in Savin Hill at 3 a.m. on Dec. 1. The victim fled in his vehicle and was not hurt.

Sexton said that the public should call in tips about the incidents to Crimestoppers at 1-800-494-TIPS.