Police fired tear gas, trying to disperse hundreds of religious students who occupied Islamabad's Red Mosque on Friday and demanded the return of its pro-Taliban cleric, two weeks after a bloody army siege that left over 100 dead. Protesters threw stones at an armored personnel carrier and dozens of police in riot gear on a road outside the mosque. After protesters disregarded police calls to disperse peacefully, police fired the tear gas, and scattered the crowd which mostly fled back inside the mosque compound. A voice on the mosque loudspeaker - where a small group of religious students appeared to be in control - appealed for the protesters not to attack security forces, but the situation remained tense. The clashes spoiled a government attempt to reopen the mosque, which was stormed by the army July 10 after its pro-Taliban clerics had spearheaded a vigilante, Islamic anti-vice campaign that had challenged the government's writ in the Pakistani capital. Earlier Friday, security forces stood by as protesters clambered onto the roof of the mosque and daubed red paint on the walls after forcing the retreat of a government-appointed cleric who was assigned to lead Friday prayers. The protesters demanded the return of the mosque's former chief cleric, Abdul Aziz - who is currently in government detention - and shouted slogans against President Gen. Pervez Musharraf. Later a cleric from a seminary associated with the mosque led the prayers. "Musharraf is a dog! He is worse than a dog! He should resign!" students shouted. Some lingered over the ruins of a neighboring girls' seminary that was demolished by authorities this week. Militants had used the seminary to resist government forces involved in siege. In an act of defiance to authorities' repainting of the mosque this week in pale yellow, protesters wrote "Lal Masjid" or "Red Mosque" in large Urdu script on the dome of the mosque. They also rose a black flag with two crossed swords - meant to symbolize jihad, or holy war. The crowd also shouted support for the mosque's former deputy cleric, Abdul Rashid Ghazi, who led the siege until he was shot dead by security forces after refusing to surrender. "Ghazi your blood will lead to a revolution," the protesters chanted. Armed police stood by but did not enter the courtyard where the demonstration was taking place. Islamabad commissioner Khalid Pervez said police forces did not want to go inside the mosque in case it led to a clash with protesters. He said the reaction of Aziz's supporters was understandable and predicted things would calm down. Over mosque loudspeakers, protesters were vowing to "take revenge for the blood of martyrs." In a speech at the main entrance to the mosque, Liaqat Baloch, deputy leader of a coalition of hardline religious parties, the Mutahida Majlis-e-Amal (MMA), condemned Musharraf as a "killer" and declared there would be an Islamic revolution in Pakistan. "Maulana Abdul Aziz is still the prayer leader of the mosque. The blood of martyrs will bear fruit. This struggle will reach its destination of an Islamic revolution. Musharraf is a killer of the constitution. He's a killer of male and female students. The entire world will see him hang," Baloch said. Pakistan's Geo television showed scenes of pandemonium inside the mosque, with dozens of young men in traditional Islamic clothing and prayers caps shouting angrily and punching the air with their hands. Officials were pushed and shoved by men in the crowd. One man picked up shoes left outside the mosque door and hurled them at news crews recording the scene. Maulana Ashfaq Ahmed, a senior cleric from another mosque in the city who was assigned by the government to lead Friday's prayers, was quickly escorted from the mosque, as protesters waved angry gestures at him. Friday's reopening was meant to help cool anger over the siege, which triggered a flare-up in militant attacks on security forces across Pakistan. Public skepticism still runs high over the government's accounting of how many people died in the siege, with many still claiming a large number of children and religious students were among the dead. The government says the overwhelming majority were militants. Wahajat Aziz, a government worker who was among the protesters, said officials were too hasty in reopening the mosque. "They brought an imam that people had opposed in the past," he said. "This created tension in the environment. People's emotions have not cooled down yet." Security was tightened in Islamabad ahead of the mosque's reopening, with extra police taking up posts around the city and airport-style metal detectors put in place at the mosque entrance used to screen worshippers for weapons. Militants holed up in the mosque compound for a week before government troops launched their assault on July 10, leaving it pocked with bullet holes and damaged by explosions. At least 102 people were killed in the violence. Attacks by militants in northwestern Pakistan along the border with Afghanistan have surged since the siege, killing about 200 others in suicide bombings and clashes, many of them security forces.