Reports from Pakistan say police in Peshawar have detained more than 100 in raids on unregistered madrasahs.
Police told "The Express Tribune" newspaper that the operation was planned after "suspicious activity" was reported at some of the Islamic religious schools.
The paper said many of those detained were Afghan nationals.
Local residents headed to a regional police station to protest the police raids.
Reports say police used batons and tear gas to disperse the crowd.
The police raid comes not long after Interior Minister Rehman Malik announced authorities would crack down on unregistered madrasahs across the country.
Compiled from agency reports