Supporters of Imran Khan, the jailed former prime minister of Pakistan, who had marched on Islamabad leading to violent clashes with security forces were dispersed in a crackdown on Tuesday, with many fleeing the city. Four civilians were reported to have been killed by gunfire in the unrest, according to local media reports.

Thousands of protesters, led by Bushra Bibi, Mr. Khan’s wife, had gathered in the capital since Monday night. They vowed to stage a sit-in at a major town square near important government buildings, demanding Mr. Khan’s release. He has been in jail since last August on charges that his party claims are politically motivated.

Pakistan, an impoverished, nuclear-armed nation of 241 million people with a struggling economy, has been in a constant state of political turmoil since Mr. Khan’s removal from office in 2022 following a parliamentary no-confidence vote. Since then, he has accused the powerful military of orchestrating his removal and has led a protest campaign to reclaim power through public rallies.

The political crisis intensified after general elections earlier this year. Mr. Khan’s party, Pakistan Tehreek-e-Insaf, claimed victory in the elections and accuses the current civilian government of being a puppet of the military.

The crackdown by paramilitary troops and police began shortly before midnight on Tuesday. Authorities turned off streetlights at the protest venue and ordered nearby shops, cafes and markets to close. The protesters, most of whom had come from the neighboring Khyber-Pakhthunkwa province, quickly dispersed as security forces used tear gas and rubber bullets, officials said. Mr. Khan’s supporters claimed that security forces had opened fire on the protesters, which the security officials deny.

By 1:30 a.m. on Wednesday, Interior Minister Mohsin Naqvi appeared before journalists at the protest venue and announced that the area had been cleared. Officials said at least 500 protesters were arrested.