Thousands of Imran Khan supporters marched closer to the capital of Islamabad on Monday demanding his release from prison as authorities braced to prevent the crowd from entering the city.

Pakistani authorities arrested over 4,000 supporters of Imran Khan, including five parliamentarians, ahead of a rally demanding the release of the former prime minister from prison, where he has been held for over a year.

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.