"Promise me, if something were to happen to me, you will take revenge from Nawaz Sharif," Khan said while addressing his supporters before starting his march towards the Red Zone that houses important government buildings including the Parliament House, Prime Minister House, President House, the Supreme Court besides embassies of various countries.
Unfazed by army deployment, the Pakistan Tehreek-i-Insaf chief and Qadri marched towards the Parliament demanding Prime Minister Nawaz Sharif's resignation, putting the PML-N-led government on the backfoot.
Police baton-charged Qadri's Pakistan Awami Tehreek (PAT) protesters as they neared the Parliament.
Anti-government protesters entered the Red Zone, even as clashes took place between them and the police at Serena Chowk where they removed shipping containers, Dunya TV reported.
Police was not putting up stern resistance and slowly retreated as part of policy to avoid violence.
"PM just told me he has ordered the police not to use any kind of force against the protesters as women & children are in the front rows," Sharif's daughter Maryam Nawaz Sharif tweeted.
The protesters of Khan and Qadri started separately but later were moving towards the Parliament together.
Information minister Pervaiz Rashid told Geo TV that the marchers have violated written commitment that they will not enter the Red Zone.
"They have women and children with them. So the government has decided to show maximum restraint. They want dead bodies but we will not give them the opportunity despite provocations," he said.
Red alert was issued at capital's Polyclinic Hospital and Pakistan Institute of Medical Sciences (PIMS), the two leading state-run medical facilities. Arrangements for additional medicines, emergency operations and extra beds were also made at the two hospitals.
"I'm coming! I'm coming to hold you accountable!" Khan said, as his vehicle progressed towards the Red Zone.
Anti-government protesters were armed with wire cutters and cranes accompanied them to remove containers.
Prime Minister Sharif has said he will not resign under any circumstance, Dawn News reported quoting sources.
As the protesters marched towards the Parliament, Sharif was present inside the official residence in the 'Red Zone' along with senior leaders of his ruling PML-N party. He is personally keeping a tab on the developing situation.