Pakistani security forces have pulled back from a radical mosque in Islamabad despite expectations of a storming operation after authorities failed to secure the release of two police officers held hostage inside.
Police and paramilitary troops had blocked vehicle access to the Lal Masjid, or Red Mosque, and bulldozers were brought up as efforts to end the standoff appeared to fall apart.
Unconfirmed reports said thousands of special police, elite forces and rangers were stood ready for deployment, with many of them gathered at the city sports complex located close to the mosque.
An army officer at the scene said units were on "red alert." But a Western diplomatic security adviser in Islamabad said the build-up of forces was likely intended to strengthen the government's hand in further negotiations rather than signalling an imminent attack.
The state-run PTV channel cited city government officials as saying there was no intention to storm the mosque, but hardline mosque clerics said they were braced for trouble.
"We expect an operation by the police and intelligence agencies. We will defend ourselves," Abdul Rashid Ghazi, who runs the centrally located complex with his brother, said. But he added that the students would not "resort to excesses."
More than 10,000 students are enrolled at the mosque's two affiliated madrassas. Automatic weapons are known to be kept on the premises and the clerics have threatened a wave of suicide bombings if action is taken against them.
The mosque administrators said on Sunday evening that they had broken off talks with the authorities after police arrested more than 150 students during the day.
"On the one hand the government is negotiating and on the other hand it is extra-judicially kidnapping our students," Ghazi said. "Talks are not possible in such circumstances."
A few hundred students of the mosque mounted extra security around the site, which is located near government and administration buildings as well as diplomatic missions.
The mosque on Saturday freed two of four police officers abducted on Friday in return for the agreed release on Monday of four students it said had been detained by the police on false charges. The deal was also thought to include a rights activist involved in missing people's cases.
Ghazi has said the other two policemen would remain in captivity until the rest of a group of 11 were freed.
Security forces surrounded the mosque after the officers were abducted Friday, but senior interior ministry officials decided to negotiate rather than storm the building.
Many Pakistanis view the attempted hostage exchange as a further government climb-down before the clerics, who in recent weeks have taken their hardline interpretation of Islam onto the streets of the capital, harassing store owners and abducting alleged prostitutes under a morality campaign.
Two police officers were also seized for a short time in March.
Baton-wielding female students have also occupied a children's library since January in protest at the demolition of illegally-built mosques in the capital, while the clerics set up a self-styled Islamic court on the mosque premises.
The government's apparent inability to deal with growing militancy in the capital has further undermined the authority of President Pervez Musharraf, who is currently embroiled in a standoff with the opposition and supporters of suspended Chief Justice Iftikhar Chaudhry.