Cricketer-turned -politician Imran Khan told his supporters that FIRs would be registered against the Sharif brothers and the interior minister for murder as clashes continued in the Pakistani capital city between police and supporters of PTI party and Tahir-ul Qadri's Pakistan Awami Tehreek (PAT) party.
He said Sunday was a decisive day and he would continue to fight till his last breath, Geo News reported.
Police have arrested over 500 workers.
The clashes broke out Saturday night when supporters of the PTI and PAT started marching towards the Prime Minister's House to stage a sit-in there, Xinhua reported.
Qadri claimed his party's seven workers were killed and many others were seriously injured when police fired steel and rubber bullets on the demonstrators.
Imran Khan said one of his workers was killed and scores of others were injured in the clashes.
However, Defence Minister Khawja Asif rejected the claims by the opposition leaders, saying no one was killed in the clashes.
Officials, however, confirmed that 240 injured people, including six children and 40 women, were shifted to Pakistan Institute of Medical Sciences while 210 others - among them five children and 25 women - were shifted to Poly Clinic Hospital.
The injured also included over 40 policemen and six journalists.
The protest leaders said that clashes broke out when police burst teargas shells to disperse the protesters marching in the capital's high security area Red Zone towards the Prime Minister's House for staging a sit-in.
However, the country's Interior Minister Chaudhry Nisar said the protesters were carrying clubs in their hands and were aiming to enter sensitive government buildings.
During the clashes, some protesters also entered the Parliament House by breaking its outer barrier.
The PTI leadership has announced a countrywide protest Sunday against the incident, while some other parties have supported the call.
Another opposition party, the Muttahida Quami Movement (MQM), demanded the immediate resignation of Prime Minister Nawaz Sharif.
Following the clashes, party workers of the PTI and PAT started protests and blocked main roads in other major cities, including Rawalpindi, Lahore, Faisalabad, and Karachi.
Thousands of Qadri and Imran Khan supporters started two separate long marches from Lahore Aug 14 and reached Islamabad Aug 15. Both parties have held talks with the government for their demands but the talks remained deadlocked.
Imran Khan, whose PTI party has 34 seats in the lower house, alleges Sharif rigged in the 2013 general elections. He has been demanding a probe by apex court and re-elections.
Qadri's supporters have been protesting for their 10-point agenda, including prime minister's resignation and the registration of a murder case against 21 people, including Nawaz Sharif and his brother, over June 17 police firing in Lahore's Model Town area.