A massive manhunt is underway in Vancouver for the person police say has sexually assaulted six women on the University of British Columbia campus as they walked home alone in the early hours of the morning.

The disclosure Tuesday by the RCMP that they believe a single suspect is responsible for not just three attacks this month but three more – the most recent last Sunday – is deepening the climate of fear on the 400-hectare campus.

The situation has prompted the deployment of police bike-patrol officers, dog-services officers and members of the Emergency Response team. Profilers and crime analysts are also on the case, struggling to provide investigators some deeper sense of a suspect described by witnesses and victims as Caucasian, in his mid- to late-20s or early 30s, with a thin build, between 5-foot-8 and 6-foot-2 tall.

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"These attacks seem to be crimes of opportunity where the suspect is specifically targeting lone females in somewhat secluded areas," RCMP Sergeant Peter Thiessen told a news conference on campus.

"In all situations, the women were assaulted while walking on the campus late into the evening or into the early morning hours," Sgt. Thiessen.

He said he doesn't recall "a similar set of circumstances on a campus or at an educational facility in this province."

Elsewhere in Canada, university administrators contacted Tuesday by The Globe and Mail said the alleged serial nature of the crimes was unusual.

The three attacks had prompted various university measures, including boosted security patrols, increased campus lighting and the distribution of safety whistles, but officials said they are going further. As of Tuesday, the school posted security officers at each of six key residence complexes on campus, launched a volunteer service to provide escorts for students in residence, and offered counselling.

"This is a stressful time for many people on our campus and in this area of the city," Louise Cowin, a university vice-president sitting alongside Sgt. Thiessen, told the news conference. "This latest news will add to the anxiety. That fear is understandable but it is also critical to act and act decisively." She added: "This is not a time to give in to fear."

On Tuesday, police linked attacks in April and May to the previous three, then added an incident that occurred at about 1:30 a.m. Sunday. An attacker grabbed a young woman from behind, police said, but she managed to scare him off by flailing her arms. Police said it took a few days to disclose the latest attack for investigative reasons.

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In one October attack, a man rushed out of a wooded area and tried to drag a 17-year-old into the trees, punching her in the face before she managed to break free.

While Sgt. Thiessen said police are confident about tracking down the suspect, he expressed another worry. "In this type of investigation, escalation is always a concern," he said.

Tips are key, he added. "Somebody knows something about who this individual may possibly be," he said. "All we need is that little piece of information that will point us in a direction of a particular individal."

The situation was the talk of the campus. "I generally feel really safe around UBC, but it is really crazy this would happen," said Celina Fletcher, an environmental science student, who said she would leave the campus before nightfall until the situation is resolved.

Nearby, arts students Kristin Weaver and Hana Decolonogon were checking a laptop awaiting a university advisory on the situation.

"I hope that they catch this guy soon," said Ms. Weaver, who lives on campus. "I think people are shocked that this number of things are increasing so quickly."

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Ms. Decolongon said the situation has had an impact. "I don't think it's an unsafe environment," she said, "but it definitely makes you feel uneasy."

With a report from James Bradshaw in Toronto