Boston police have increased patrols in East Boston and are asking the community to remain vigilant after three women were attacked in separate incidents on Monday. Two of the three incidents were sexual assaults, and authorities said they believe the attacks may be connected. The first two assaults occurred after 4:30 p.m. on Trenton Street, about 20 minutes apart and involved a man wearing all black, who had a medium build, a mark on his cheek, and smelled of alcohol. The third was around 8 p.m. on Chelsea Street. A woman said she was approached from behind by a man wearing all black. The victim said she was shown a knife, and man attempted to sexually assault her, police said in a statement. One woman was taken to a hospital, but the two other victims refused medical attention, police said.Derek J. Anderson can be reached at email@example.com.