Hundreds of Islamist groups returned to Rabaa al-Adaweya Square in Nasr City, Cairo, on Friday morning ahead of mass protests in support of President Mohamed Morsy.
Islamist officials said the protest would continue until 30 June.
Muslim Brotherhood spokesperson Yasser Mehrez announced that Rabaa al-Adaweya protesters would stage a sit-in until Sunday.
Mehrez told the official Freedom and Justice Party (FJP) newspaper on Friday evening: "The sit-in will be peaceful and aims to stress the principles of constitutional legitimacy and emphasize the importance of and need to preserve state institutions, and complete what is not completed."
Tens of thousands of protesters joined the protest on Friday, dubbing it "Legitimacy is a red line," aiming to defend the beleaguered president, Morsy.
Participants called to protect constitutional legitimacy and resist any attempt by perceived remnants of ousted president Hosni Mubarak’s regime to hijack power and drag the country into chaos.
The protesters set up a huge stage in front of Rabaa al-Adaweya Mosque with loudspeakers, as well as erecting 8 tents to protect them from the hot Friday sun. They said they were ready to engage in an open-ended sit-in at the end of the day, though the plan was still under consideration.
Journalists and street vendors also turned up in force.
Two military helicopters surveyed the Islamist demonstration from above.
The General Directorate of Cairo Traffic set dozens of iron barriers on the al-Nasr and Tayaran streets, leading to Rabaa al-Adaweya Square, and diverted traffic away from the area.
The Ministry of Health and Population distributed ambulances around Rabaa al-Adaweya Square for emergency cases.
Among the groups participating in the Nasr City rally are the Muslim Brotherhood's Freedom and Justice Party, Jamaa al-Islamiya's Construction and Development Party, the Salafi-oriented Asala Party, the Salafi Watan Party, and others.
Edited translation from Al-Masry Al-Youm
