Footage on television showed policemen in riot gear firing in the air and using batons to push back dozens of supporters of Qadri, who lobbed stones at them.

Interior Minister Rehman Malik told the media that security forces fired in the air after Qadri's supporters pelted them with stones.

Qadri's spokesman Shahid Mursaleen claimed in an email statement that trouble erupted after police tried to arrest the cleric. "Once they realised that the crowd is not letting them come near him, they (police) opened fire in the air which lasted for 10 minutes," he claimed.

Mursaleen further claimed police fired at Qadri's car andtried to smash its windows. "The crowd ran after the police with sticks when they realised the police (was trying) to attack their leader. The police ran away," he said.

His claims could not be independently confirmed. The spokesman said Qadri, who was in a portable shelter, was safe.

Qadri, who heads the Tehrik Minhaj-ul-Quran, marched into Jinnah Avenue in the heart of Islamabad with tens of thousands of supporters and gave the government hours to quit and to dissolve the national and provincial assemblies. He declared

that he was leading a "people's democratic revolution".

The cleric's party had signed an agreement with the Islamabad administration to hold a peaceful protest a few kilometres from the National Assembly, but the cleric surprised authorities by inciting his followers to remove barricades and move towards a square near parliament Qadri also incited policemen and paramilitary personnel to defy their officers, saying the officials would be removed by tomorrow.

Pakistan's political circles have been surprised by the sudden re-emergence of Qadri, a Canadian national who has lived outside the country for the past seven years.

A fringe player in Pakistani politics who was involved in several controversies in the past, Qadri returned from abroad last month after his party ran a multi-million rupee advertisement campaign in newspapers and on television.

Qadri subsequently addressed a large gathering at the Minar-e-Pakistan in Lahore on December 24 and gave the government time till January 10 to carry out electoral reforms.

At the time, he had warned he would march to Islamabad with his followers on January 14 and stage a sit-in till his demands were met.

The ruling Pakistan People's Party, main opposition PML-N and other major parties have accused Qadri of acting a front for the security establishment and foreign elements to delay the general election scheduled to be held by May so that that