The incident took place when the civic body started a drive to remove encroachments near telephone exchange area, following which the agitated activists of Sri Guru Ravidas Committee started protesting against the authorities, police said.
They entered the municipal council office and indulged in vandalism by breaking office furniture, they said.
The activists also blocked traffic near the bus stand.
On receiving information about the incident, police reached the spot and resorted to lathicharge to disperse the mob and also arrested some persons who were involved in damaging the property.
However, municipal council Executive Officer SK Gulati said they have served the notice several times to remove encroachment but since it was not done, the council today initiated the process to remove it following a court order.