Thousands of supporters of Pakistan’s imprisoned former premier Imran Khan have defied a lockdown and mass arrests to head to the capital to demand his release.

A march by hundreds of supporters to demand the release of jailed former Prime Minister Imran Khan reached the fringes of Pakistan's capital of Islamabad on Monday, his party and officials said, amid reports of violence elsewhere.

Pakistan's capital, Islamabad, is under lockdown for a second day as thousands of protesters demanding the release of former prime minister Imran Khan from jail converge on the city. His supporters are also calling for the overturning of election results they say were rigged - a claim disputed by the government.