Northeastern University officials are urging the campus community to be vigilant after two students reported they were robbed at knifepoint Saturday night. The students said they were walking at about 10 p.m. near West Village G, an on-campus dormitory, when two males, described as black juveniles wearing dark clothing, asked them what time it was, according to a campus advisory e-mailed by the university’s public safety division. When the students pulled out their cellphones to check the time, the juveniles allegedly stole the phones, and one of the suspects brandished a knife before they ran toward the MBTA’s Ruggles Station. “Members of the NU community are urged to be aware of this tactic and to be cautious of their surroundings while walking outside in public areas,” the campus advisory said.Matt Rocheleau can be reached at firstname.lastname@example.org. Follow him on Twitter @mrochele.