ISLAMABAD, Pakistan - Female Islamic students wearing black burqas kidnapped an alleged brothel owner and held her prisoner at their seminary in the Pakistani capital yesterday, part of an anti-vice drive in defiance of the military-dominated government.

In a separate sign of growing extremism in Pakistan, pro-Taliban fighters firing rockets attacked a northwestern town and kidnapped the principal of a school where they had tried and failed to recruit students as suicide attackers. One security-force member was killed.

Both incidents reflect an undercurrent of fundamentalism that is challenging the moderate mainstream society in this Muslim nation of 165 million people, and the failure of President Pervez Musharraf's government to contain it.

Late Tuesday, a group of 30 female and 10 male Islamic students broke into the alleged brothel in Islamabad after the owner, known as Aunty Shamim, ignored their warning to close it.

One of the students, Seema Zubair, 20, said they were holding Shamim, her daughter, her daughter-in-law, and her 6-month-old granddaughter inside their Jamia Hafsa seminary. She said they were not being maltreated and would be freed if they promised to close the brothel.

"We are not authorized by the government to arrest them, but we are authorized by our religion, because this is evil," Zubair told the Associated Press.

Authorities yesterday arrested two of the seminary's female teachers and two male students over the abductions, sparking protests by hundreds of stick-wielding students outside the Lal Masjid mosque where they worship. Abdul Rashid Ghazi, vice principal at the Jamia Hafsa seminary, threatened jihad, or holy war, unless the teachers were freed.

Both male and female students roamed the main road near the mosque, yelling "Down with Musharraf!" while jihadist slogans and songs played over loudspeakers. Male students commandeered two police vehicles, beat an officer with sticks, and captured two other policemen, witnesses said.

Tensions eased late yesterday, when Ghazi announced the policemen would be freed after authorities agreed to release the seminary teachers and male students.

Meanwhile, in the town of Tank, about 185 miles southwest of Islamabad, pro-Taliban fighters launched a raid in revenge of Monday's police shooting of two men who were accused of trying to recruit teenagers for holy war and suicide bombings from schools in the area.

Local police chief Omar Hayyat said hundreds of fighters fought an hours-long gun battle with security forces, killing one paramilitary policeman.

The militants abducted Farid Ullah, the principal of the Oxford Public School where Monday's fighting took place, and one of his brothers, Hayyat said.

The militants later fired rockets at a police station and other nearby government buildings and set two banks on fire.