Students at a mosque in Islamabad, the capital of Pakistan, have seized four police officers demanding the release of 10 other students held by intelligence agencies.
Armed police have taken up positions outside the Red Mosque compound while students armed with batons blocked some nearby roads.
"We have made it clear to the government that we will not free the policemen until the release on bail of our students, some of them arrested on false charges of burning video CDs," Abdul Rashid Ghazi, the mosque deputy, said.
He also threatened nationwide reprisals if a police operation is launched against the mosque or madrassa.
"We are not mistreating the policemen that we have in custody. We are offering them good food and they are comfortable with us," Ghazi added.
Police and district administration officials have been allowed into the mosque for talks in an attempt to secure the release of the policemen.
An interior ministry official said the government wanted a "peaceful solution to the row through negotiations."
Last month the Red Mosque set up a self-styled Islamic court which issued a religious decree against the country's female tourism minister for hugging a French paragliding instructor after a charity jump.
The mosque's students have also launched anti-vice patrols targeting music and video shops.
They also abducted three women they accused of running a brothel and forced them to confess in front of reporters before releasing them.
In an interview aired after the plainclothes officers had been captured on Friday, Pervez Musharraf, the Pakistani president, said that religious extremism was on the rise and the government needed to "strongly counter it".