Boston police issued a warning after multiple people in the Dorchester neighborhood were robbed of their cell phones.
Police said on Monday that there have been four reported robberies since the start of the month.
In most of the robberies, the suspect used a knife or scissors to threaten and rob the victims who were out walking.
The most recent robbery took place just after midnight Sunday. Police said a woman walking from the JFK MBTA station was approached from behind by two men and felt something hard in the back of her head. The men demanded her money and cell phone, which she gave them before they fled.
The other robberies took place on Nov. 2, 4 and 6.
Police said they are investigating. They urged people to keep their phones out of sight, never walk with earphones in and pay attention to their surroundings.