DENVER -- Police credit an increased number of patrols and a new tactical plan for stopping a series of assaults in Boulder, authorities said Friday.

At least six college-aged women have been assaulted in the University Hill and Gross-Grove areas since Halloween. Four were sexually assaulted, said Boulder police spokeswoman Sarah Huntley.

All of the victims were college-aged women who were attacked by a stranger.

In the most recent attack on Dec. 5, a woman told police a man accosted her, climbed on top of her and tried to strangle her, Huntley said.

The woman told police she kicked him in the groin and hit him in the face. She then ran to a friend’s house for help, police said.

The same day Police Chief Mark Beckner initiated a plan to re-assign officers and increase patrols. "Officers were directed to conduct high visibility patrols, make numerous contacts, light up alleys and assist women in getting home safely," Huntley said.

The department has assigned more detectives to follow tips, she said.

"With the close of the semester yesterday and no additional reports of assaults, the tactical plan has been successful," she said.

"Making it to the end of the current semester without any further attacks in these areas was our No. 1 priority," Beckner said. "We are very pleased to have reached that goal and will continue to put great effort into identifying the suspects in the prior attacks."

Police said descriptions of the attackers have varied, making it difficult to determine whether the assaults are connected.

While most students will be out of town for the winter break, Boulder police will continue patrols and have asked the public to report suspicious activity.