Boston and MBTA Transit Police are stepping up patrols after seven robberies of women walking from Red Line stations in Dorchester, Boston police said Thursday.

The women were robbed ­after leaving the JFK/UMass, Savin Hill, Shawmut, and ­Ashmont stations, Boston ­police said. The crimes happened between 7 p.m. and 10:30 p.m. during the past two weeks, police said.