A woman was grabbed and groped Monday evening by an unknown man who ran off when she screamed, police said.

The 32-year-old woman left the Davis Square T stop at about 8 p.m., left through the Holland Street side and was walking up Dover Street toward Cambridge while talking on the phone when she was grabbed from behind, police said. “The victim turned around, saw the suspect and screamed while running into the street,” according to a neighborhood alert.

The man, described as being black, about 6 feet tall and wearing all-black clothing and a black baseball cap, ran toward Davis Square.

Somerville police are investigating the indecent assault and battery, which Cambridge police clarified means “an unwanted touch or groping.” They said they have added patrols of marked and unmarked cruisers in the area and asked people to call 911 immediately if they see anyone “with a suspicious manner or appearance.”

They advised people walking alone, especially women, to walk on well-lit routes whenever possible, avoid wearing headphones or earbuds and to stay aware of their surroundings, keep a phone handy but avoid distracting calls and, if someone is following, to get to a lighted area with other people. “Trust your instincts and avoid whatever feels to you like it could be a potentially dangerous situation or environment,” police said.

Anyone with information is urged to call Somerville Police at (617) 625-1212 or text 617SPD to Tip411.