Authorities warned pedestrians around Allston and Brighton to be vigilant following reports of four street robberies and another attack over the past five days.
Three of the robberies involved two or more suspects, one of whom had a knife, officials said.
Those incidents were reported in the Allston Village area between midnight and 1:30 a.m., according to an alert Boston University Police posted to their website Friday citing information from Boston Police.
The other robbery was an unarmed purse snatching, the alert said.
There was also an incident in which a female victim said she was knocked down from behind but that the suspect did not try to take anything from her, police said.
The string of attacks began on Monday, March 18. All five incidents were reported within the D-14 Boston Police district, which is comprised of the city's Allston and Brighton neighborhoods that are popular to students who attend area colleges including BU.
At the beginning of each of the past two semesters, a string of robberies was areported near BU's campus. Last fall, several assaults against female students were reported in which victims said they were pushed to the ground by someone who then took a photo under their skirts.
E-mail Matt Rocheleau at firstname.lastname@example.org.
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