In what analysts here called an unprecedented reversal by security forces, riot policemen in Lahore melted away rather than continue to confront protesters who had rallied around Nawaz Sharif, when he defied a house arrest order early on Sunday.

By early evening, the sight of exuberant anti-government crowds in Lahore—a mix of Sharif loyalists, supporters of smaller opposition parties and ordinary people with their young children—encouraged people in other cities in Punjab to come out on the streets.

Sharif headed toward Islamabad in a long convoy of cars, with supporters lining up to greet him all along, said Ahsan Iqbal, information secretary of the Pakistan Muslim League-N. He added that party workers armed with cranes were removing shipping containers placed as roadblocks by the police at junctions along the route. Speaking to Geo Television by phone from his car, Sharif said, “This is a prelude to a revolution.”

Sharif began the day under house arrest at his home outside Lahore, hemmed in by barbed wire and security roadblocks. But he denounced the crackdown as illegal and said he would move to address an Opposition demonstration at the city center and continue with a national opposition march on the capital planned for Monday. He left his house in a convoy of cars that broke through a ring of police barriers. Soon his convoy was joined by truckloads of supporters and, with the help of sympathetic police officials, was able to move slowly toward the area around the General Post Office building, where riot police and protesters began scuffling.

But by 5 pm, the police disappeared and huge crowds, on foot and in cars, enveloped the Mall. Green, red and white banners of with portraits of Sharif were held aloft as other groups, including Jamaat-i-Islami, a right wing Islamist group, joined what turned into the anti-government demonstration that the Government had feared all along.

A senior officials in the Lahore government, Chief Magistrate Sajjad Bhutta told reporters he refused to carry out what he called the illegal acts of the police crackdown. He appeared among the crowds, surrounded by cheers and waving flags.

Aitzaz Ahsan, the leader of the lawyers’ movement, said protesters would try to defy the government’s efforts to keep them away from Islamabad and attempt to converge on the capital from various points on Monday. “The strategy is simple,” he said. “The long march is on for an indefinite period.”

There appeared to have been a decision, either by provincial officials, many of whom support Sharif, or at the national level, to allow Sharif to proceed. In Islamabad, Farahnaz Ispahani, a spokeswoman for President Asif Ali Zardari, said the detention orders for leaders of the PML-N had been issued for the sake of their security. “The Government cannot be responsible for someone inflaming crowds... It’s not a mature move. From a security view we don’t think this is a wise move,” she said.

“This is the first time in the history of Pakistan that the police and civil administration have defied orders by the Government to control public demonstrations,” said Ashtar Ali, a corporate lawyer who supports Sharif’s Pakistan Muslim League-N. “The writ of the Government has failed.”