The 42-year-old constable molested the girl while she was on her way back home after attending college, the police said.
A mob chased the accused Narottam Bal, who was drunk, as the girl raised an alarm.
As the news spread, the agitated students from nearby Derabish College rushed to the police station demanding immediate arrest of the culprit. As tension mounted, the constable was arrested.
The accused was sent to jail with a local court rejecting his bail plea.