Tens of thousands of supporters of toppled president Mohamed Morsi have flocked to Rabaa Al-Adawiya Mosque in north-east Cairo where a mass rally is being held on Friday to push for the Islamist leader to be reinstated.

The broad intersection where the demonstrators are gathered was already filled up early on Friday, ahead of afternoon prayers. A protester told Ahram’s Arabic-language website that demonstrators from across Egypt had been flocking to the rally since Thursday night for fear of imminent road blocks to bar them from joining the mass protest.

Significant numbers of Morsi’s supporters have been camped out at Rabaa Al-Adawiya since 28 June, initially holding a sit-in to oppose calls for Morsi to step down, and following the Islamist president’s ouster on 3 July, demanding his reinstatement.

Protesters waved flags as patriotic and pro-Morsi songs were played on the main stage. On the stage, big banner reading “anti-coup” in English was displayed. An imam gave a Friday sermon to the gathered crowds, in which he mourned the “Islamist martyrs” and urged those assembled to continue their sit-in.

Monday saw deadly violence outside the nearby Republican Guards headquarters, when clashes between the armed forces guarding the location and pro-Morsi demonstrators lead to the death of at least 51 people, including one soldier.

Islamist preacher Safwat Hegazy gave a speech on the main stage in Rabaa Al-Adawiya in which he vowed that protesters would never call off their protests until the president is back in office, or would "die as martyrs," affirming that the army would bow to pressure "whether they want to or not."

In Giza, marches from the districts of Al-Omraniya and Dokki have set out towards Nahdet Misr Square, another venue where Islamists have been encamped to defend the former president’s “legitimacy.”

Several marches to the Giza square, called for by a pro-Morsi coalition of several Islamist parties, are planned for Friday afternoon.

The former president’s supporters from Cairo and other provincial towns started gathering there on Thursday night, Ahram Arabic reported.

Groups who oppose former president Morsi, who was removed by the army on 3 July after millions took to the streets to demand his removal, have also called for mass gatherings on Friday.

The National Salvation Front, the Rebel campaign, and the 30 June Front have called for public gatherings at Tahrir Square and the Ittihadiya presidential palace and celebrations of the iftar meal, which during Ramadan is eaten after sunset, at the iconic locations.

At least 90 people have been killed and almost 2,000 injured in unrest over the past week, heightening polarisation during the country's troubled transition to democracy.