Police on Sunday claimed to have arrested a gun-wielding man at Parade Ground where Pakistan Tehreek-e-Insaf has organised a rally to celebrate the disqualification of Nawaz Sharif by the Supreme Court.

On Sunday evening, thousands of PTI supporters streamed into Islamabad's Parade Ground waving flags and cheering as they waited for Imran to speak.

The cricket star-turned-politician, who spearheaded demands for an investigation on Nawaz Sharif after the leaking of the Panama Papers, had announced to observe a "thanksgiving day to celebrate Pakistan's victory against corruption".

On Friday, the Supreme Court disqualified Nawaz Sharif from office on the grounds he did not report a nominal monthly salary from his son's Dubai-based company, money the former prime minister says he never received.

For all the furor over Nawaz's ouster, the immediate balance of political power in Pakistani is unchanged.

His PML-N party hold a healthy majority of 188 seats in the 342-member parliament, and it is expected to swiftly install an interim prime minister on Tuesday and later elect Nawaz Sharif's younger brother, Shahbaz, as leader.

The confirmation from parliament came after President Mamnoon Hussain convened a special session following Nawaz Sharif's decision to put forward his ally Abbasi as interim leader and named his brother Shahbaz, 65, as long-term successor.

The turmoil and the premature end to Sharif's third stint in power has also raised questions about Pakistan's democracy as no prime minister has completed a full term in power since independence from British colonial rule in 1947.