BERKELEY -- The armed robbery of a UC Berkeley student as he walked alone on a pathway Tuesday morning marked the fifth robbery or attempted robbery on or near campus in less than a week, authorities said.

The latest victim, a young man walking north on a pathway between North Gate and University Drive in the area known to students as "Cardiac Hill," was approached from behind about 7:10 a.m. by two men who demanded he give them his backpack, UC Berkeley police Lt. Eric Tejada said.

The student spotted the handle of a black handgun in one suspect's pocket, and gave his belongings to the men, who took off on foot toward Hearst Avenue.

While none of the victims in any of the incidents reported since Thursday were seriously injured, Tejada said, police were stepping into high gear to ensure peace of mind for people walking on campus.

"They may not have been hurt physically, but obviously it's a pretty traumatic event emotionally," he said.

The spree started Thursday, when a 57-year-old visitor to the campus was grabbed from behind by an armed gunman while walking near the intersection of Berkeley Way and Oxford Street about 5:30 a.m. The man demanded money and then hit her when she told him she didn't have any, police said.

About 14 hours later, a 19-year-old student awaiting a shuttle stop at 7:45 p.m. on the sidewalk of Beverly Cleary Hall at 2424 Channing Way was approached by a man who shoved her and took her cellphone.

Then, on Saturday at 12:40 a.m., three men tried to rob a student of his backpack on Campanile Way between Dwinelle Hall and the Valley Life Sciences Building, but the student held on to his belongings through the struggle, Tejada said.

On Sunday at 9:11 p.m., a man pointed a handgun at a student near Moffitt Library on University Drive before throwing him to the ground and taking his cellphone.

The descriptions of the suspects in four of the five robberies were similar to the one reported Tuesday, Tejada said.

The first suspect in that case was described as a black male between 18 and 20 years old, about 5-foot-10 with a medium build and facial hair, wearing a black hooded sweatshirt and black pants. The second suspect, who was carrying the black handgun, is a black male, between 20 and 23 years old, about 6 feet tall with a slender build, wearing a black hooded sweatshirt and black pants.

"We're trying to determine whether they're the same suspects" as in three of the other cases, Tejada said.

The robbers in the Saturday morning incident were described as three Asian males in their late teens or early 20s.

In light of the recent robbery string, UC Berkeley police have deployed extra uniformed and plainclothes officers on campus, Tejada said. And while the recent robberies suggest an alarming trend, Tejada adds that robberies on the whole are down for the year.

"We crunched the numbers and this year we had about half the amount of robberies we had last year," Tejada said. "But seeing so many in just a few days is pretty troubling, so that definitely got our attention."

Tejada also noted that both incidents Thursday occurred off campus on adjacent property, and are not included in the university's year-to-date totals.

"People need to be aware of their surroundings, and that includes not talking on their cellphones, looking at their phone, and not having earbuds in," Tejada said. "I'm not saying that's what happened in these cases, but a lot of times, victims are busy looking at their phones."

Campus police remind students to trust their instincts when walking on campus, and advise them to only travel well-lighted paths at night. Also, students can call the campus BearWALK service at 510-642-WALK to have a radio-equipped escort walk them to nearby residences, parking lots and public transportation from nightfall until 2 a.m. Anyone with information about any of the recent robberies at UC Berkeley may contact campus police at 510-642-6760,

Contact Erin Ivie at eivie@bayareanewsgroup.com. Follow her at Twitter.com/erin_ivie.