A third sexual assault by a stranger in as many weeks has Minneapolis police and an expert on sexual violence calling for increased efforts to protect women.

The latest attack on a woman walking alone occurred shortly after 2 a.m. Saturday near E. 34th Street and Chicago Avenue S., where a 33-year-old Minneapolis woman had just gotten off the Route 5B bus from downtown Minneapolis on her way home, police said.

A man, who apparently had stalked the woman from a downtown bar, grabbed and dragged her into a secluded area near her Powderhorn Park area home, then sexually assaulted her, according to reports from police and a friend of the victim.

Sheila Gustafson said her friend had just left the Gay 90's bar when she called, worried about a man nearby.

The man took her cellphone and coat before she boarded the bus, and then got on the same bus two stops later, Gustafson added. Gustafson said she kept calling her friend's cellphone until the man finally answered and said, "Your friend is too drunk to talk," before he hung up.

Gustafson called police and then an acquaintance to tell him to check on her friend. He and two others went to the woman's neighborhood and found her after she had been assaulted and left with slap marks on her face and a bruise near her eye.

"She just ran to him hysterically," Gustafson said. "At that point, he knew it wasn't something good."

Gustafson said her friend told of being dragged to a fenced-in area near a day-care facility. Police showed the woman several photographs of possible suspects, Gustafson said. When she pointed out one man immediately, police responded that he had recently attacked another woman in a different part of the city.

There were no arrests by Tuesday night, said police Sgt. William Palmer. The suspect was described as a dark-complexioned black man, 30 to 40 years old, 6 feet to 6 feet 2 inches tall, with a thin build. He was wearing a puffy black jacket.

A suspect also remains at large in a predawn attack on Nov. 19, this one along Stevens Square Park in the 1800 block of Stevens Avenue S., where a 26-year-old woman was sexually assaulted.

"At this point, it is too early to tell if [unsolved] attacks were committed by the same person," police Sgt. Stephen McCarty said Tuesday. "Of course, the [Police Department's] Sex Crimes Unit is looking at that aspect."

Last week, registered sex offender Louis R. Oliver, 47, of Hastings, was charged with first-degree criminal sexual conduct in an attack and robbery on Nov. 19 of a female college student who was walking before dawn near the West Bank Minneapolis campus of St. Catherine University. Oliver remains jailed.

"Stranger assaults of this nature are rare," Palmer said, although city statistics weren't immediately available Tuesday.

The crime alert issued Tuesday to residents about the latest attack included strong advice from police on what women need to do to protect themselves: Be aware of strangers, avoid traveling alone (especially after dark), stay away from isolated areas, and switch directions and seek a safe place if you think someone is following you.

If confronted, draw attention by yelling, shouting commands or making other noises, police urged. Walk or run from danger to a safe place.

In general, "do what you need to do to survive," the advice from police added. "Your single most effective weapon is your own judgment."

Pamela Zeller, executive director of the Sexual Violence Center, a nonprofit that works to eradicate sexual violence and abuse throughout the Twin Cities, added that the responsibility to prevent sexual assault doesn't rest with victims, who are more likely to be assaulted by someone they know rather than a stranger.

"We don't want to give the message that it is somehow their fault that they didn't protect themselves," she said.

The community at large needs to be more alert to be able to help prevent sexual assaults, Zeller said. Zeller's organization offers active bystander training to show people how they can help prevent violence. It can be as simple as checking on an obviously intoxicated person leaving a bar with someone.

"This woman probably passed by a number of people. ... Could there have been somebody that intervened?" Zeller asked.

Anyone with information about any of the attacks should contact police.

pwalsh@startribune.com • 612-673-4482 nicole.norfleet@startribune.com • 612-673-4495