Two days later, the Supreme Court of Pakistan declared Khan's arrest illegal and ordered his immediate release.
On Friday, the court released the lawmaker on bail until 26 May. It also barred law enforcement agencies from arresting Khan in connection with any new case filed against him after 9 May until 17 May.
However, supporters of Pakistan's ruling coalition staged a sit-in in front of the Supreme Court in Islamabad on Monday to protest Khan's release from custody.
The protesters, mostly workers and supporters of the Jamiat Ulema-e-Islam-Fazl (JUI-F) party, have reached the capital's Red Zone, where government buildings are located, media reports said.
So far, police have arrested one person who stole eight cell phones from the sit-in participants, the broadcaster reported.
Following Khan's arrest on 9 May, the PTI called on Pakistanis to gather for mass demonstrations to demand the lawmaker's release. Mass protests erupted across the country, with activists torching police vehicles and damaging government property, and police using gas and water cannons to disperse the crowds.