The clashes started after orders by Khan and Qadri yesterday to shift their protest venue to the official residence of Sharif to force him resign immediately.
At least 308 injured were brought to Polyclinic and Pakistan Institute of Medical Sciences, the two premier state-run hospitals, a Pakistani channel Duniya TV reported.
Hundreds of protesters entered the lawn of parliament but they were stopped at the main entrance of the building where army soldiers were deployed.
Khan and Qadri are with protesters and exhorting their supporters to force their way towards the PM House.
Information Minister Pervaiz Rashid said that protesters had committed a crime by attacking parliament which is a "symbol of democracy".
The clashes were continuing as police pushed them back with intense shelling of tear gas and rubber bullets.
The situation was very tense in the capital as a number of demonstrators refused to budge from the protest site.
Both the leaders are agitating since August 14 against alleged rigging during the last year general elections.
"I will lead the march to the PM House. All my supporters should follow me," Khan said asking women and children to stay behind until asked by him to join the march towards the PM House.
Khan's announcement came soon after a similar decision by Qadri.
Thousands of police and paramilitary personnel were deployed blocking all the roads leading to the PM residence.
Khan asked his supporters to remain peaceful and asked law enforcement agencies not to stop the agitators.
As tension mounted, Sharif left for Lahore. A late night government announcement categorically ruled out Sharif's resignation and there is no threat to his life.