The accused, Ram Chandra, was in an inebriated state when he molested the girl last afternoon when she was standing at Khalsa College bus stand, they said.
After raising alarm, passersby rushed to the victim's help and nabbed the accused, who was beaten up by the mob before police reached the spot and arrested him.
A case under sections 354 (outraging modesty of a woman), 354A (sexual remarks) and 509 (word, gesture or act intended to insult the modesty of a woman) of the Indian Penal Code has been registered against him.