Hundreds of Pakistani human rights activists have staged a protest calling for action against a major madrassa, or religious school, in the capital.
The protesters chanted slogans against the rise of 'extremism'
About 600 people demanded curbs on "extremist forces" they said were promoting "intolerance and violence".
Last week female students from a madrassa in Islamabad abducted a woman they accused of running a brothel, holding her captive for two days.
The students said Islamic law gave them the right to stop immoral activity.
The students, from the Jamia Hafsa madrassa, seized the alleged brothel owner and two of her relatives, releasing them only when the woman had read out a confession.
Human rights campaigners said students from the madrassa were "harassing and terrorising ordinary citizens of Pakistan in the name of Islam", AFP news agency reported.
In a statement, the Human Rights Commission of Pakistan and a dozen non-governmental organisations urged people to "rise against these extremist religious bigoted forces and secure the future of the present and future generations".
The Jamia Hafsa madrassa has frequently been in the news in recent months. In February, armed students prevented the authorities from demolishing an illegally constructed mosque, and occupied a nearby children's library.
Female madrassa students have previously rallied to make their case
But correspondents say it appears the Pakistani administration is reluctant or helpless to take action against the school's teachers and students.
Jamia Hafsa and its adjoining madrassa, Jamia Faradia, are part of the Lal Masjid (red mosque) complex.
Lal Masjid has long been a problem for the capital city administration and Pakistan's President, General Pervez Musharraf.
It has often criticised his policies in the "war on terror" and called for Islamic law to be enforced in Pakistan.