They came from many parts of Egypt, most of them bused to the rally in support of Islamist President Morsi, and declared their allegiance to the president and Sharia law.
Tens of thousands of Egyptian Islamists gathered for a show of strength in Cairo on Friday ahead of planned opposition protests against President Mohamed Morsi, highlighting the tense political divide in the Arab world's most populous state.
Carrying Egyptian flags and portraits of the president, they flooded into the large square outside the Rabaa al-Adawiya mosque in the Nasr City neighbourhood and into the surrounding avenues.
Islamist groups led by the powerful Muslim Brotherhood from which Morsi hails, had called for the rally ahead of planned June 30 protests to demand an early presidential election.
Morsi has been in office for just one year.
Inside the mosque, worshippers finished their prayers and broke out into chants of "Morsi is a president for all Egyptians" before joining the crowds on the streets.
The turnout, they said, was proof that Morsi enjoyed the support of the Egyptian people.
"We are here in such huge numbers so that the secularists don't think we are a minority... We are capable of protecting legitimacy and Sharia (Islamic law)," said Hamida Bakkout, 43, holding a picture of Morsi.
Omar Mostafa, 18, who had come from the Nile Delta province of Beheira, said "this is a message that there are many of us behind the president. We don't care about the mobilisation of the opposition."
Many supporters had been bussed in to Cairo for the event, AFP reporters said.
The Islamists accuse the opposition of being remnants of the regime of ousted president Hosni Mubarak and of seeking to sow chaos.
"Democratically elected presidents are never removed through protests," Muslim Brotherhood spokesman Gehad al-Haddad said.
A campaign dubbed Tamarod (rebellion in Arabic) first called for the anti-Morsi rally to coincide with the first anniversary of his becoming president.
Egypt is, quite literally, falling apart. It's economy cannot survive without massive foreign investment. And that's just to keep the people from starving to death. Any thought of economic reform by Morsi cannot be realized because, simply, there's no economy to speak of.
The opposition is kidding itself if it really believes they can get the Brotherhood to call for an early presidential election. They've already postponed the parliamentary elections. Why would they move up elections for president?
The Muslim Brortherhood has the power and they're not going to give it up without a fight.