The University of British Columbia has issued a safety alert, after a spate of disturbing sexually-motivated attacks by men on campus.

The most recent reported incident took place Sunday at 3:30 a.m. PT in a residential area, when a man came out from under a stairwell within an apartment building in the 2700 block of Fairview Ave. and accosted a 20-year-old woman.

She told police he started trying to take her clothes off and tried putting his hand up her skirt, but she struggled free and screamed, before he ran away.

Less than a month ago, at the end of September, at 2:45 a.m. PT on a Saturday, a man - who may or may not be the same person - also tried to grope a 19-year-old woman under her skirt.

The woman was walking alone in the 6300 block of Biological Sciences Rd. when he came up behind her and tried to pick her up and pull her into a garden area. When she broke free and screamed, he fled on foot.

In April of this year, someone grabbed an 18-year-old female student, throwing her to the ground, near Pacific Spirit Park's Trail 3, while she was out jogging at around 6:30 p.m. PT.

She was not sexually assaulted or robbed, police say, but the motive for the attack remains unclear.

Last spring, in April and May, police warned the campus community about two other nighttime groping incidents, in which a male suspect reached up under the skirts of a 20-year-old woman and a 36-year-old woman, grabbed their buttocks and then ran off.

Police say there are some similarities between the two most recent attacks, but can't say for certain whether they are connected to the attacks and assaults that happened on or near campus earlier this year, or the year before.

The latest string of attacks follow another spate of gropings in 2010, when police again issued warnings to the campus community.

With files from the CBC's Belle Puri