Senior Superintendent of Police Prahlad Meena said the madrasa and mosque were located on illegally encroached government land and the demolitions were carried out in the presence of police and Provincial Armed Constabulary (PAC) personnel, in compliance with a court order.
Large numbers of angry residents, including women, took to the streets to protest the action as demolition of the two structures began.
They were seen breaking barricades and arguing with police personnel participating in the demolition exercise.
As a bulldozer razed the madrasa and mosque, mobs pelted stones at police personnel, municipal corporation workers and journalists, officials said.
The police attempted to disperse the angry crowd by resorting to a mild lathi charge and firing tear gas grenades.
However, tension increased and the mob set fire to several vehicles, including a police patrol car, they said.
By late afternoon, tension increased further and the Banbhoolpura police station was also set on fire, leading to the imposition of a curfew in the city, they added.
The injured were admitted to Soban Singh Jeena hospital here, officials said, adding that most of them suffered head and face injuries.