Court agrees to hear appeal while Bhutto says Musharraf ready to quit as army chief.
Kamal Hyder, Al Jazeera’s correspondent in Islamabad, said the lawyers were determined to bring an end to army rule and restore democracy.
He said an invigorated judiciary posed a serious challenge to Musharraf.
The protests came as lawyers of Musharraf told the Surpreme Court that his current presidential term ends on 15 November.
Iftikhar Muhammad Chaudhry, the Surpeme Court chief justice, had ordered the government on Wednesday to name the date on which Musharraf’s term in office would expire.
His order came after the Supreme Court took up a legal petition, filed by the radical Jamaat-i-Islami party, which challenges a 2004 parliamentary act allowing Musharraf to be president-in-uniform.
Musharraf aims to get re-elected by the national and provincial assemblies some time between 15 September and 15 October and to hold a general election around the end of the year.
But he is facing a barrage of legal and political opposition.
Former prime minister Nawaz Sharif, who Musharraf ousted in 1999 and later sent into exile, has vowed to return on 10 September, despite the possibility of arrest on corruption charges, to mount a campaign to end Musharraf’s rule.
In the face of his deepening political problems, Musharraf has turned for help from another exiled former prime minister, Benazir Bhutto, in the hope that a power-sharing deal with her would boost his legitimacy and help him overcome constitutional hurdles to holding on to power.