More than 200,000 people crowded Tahrir Square in the capital city on Sunday waving flags and shouting for Morsi to step down.

"The people want the fall of the regime!" protesters in Tahrir Square chanted as part of the largest demonstration since Hosni Mubarak's ousting in 2011.

Huge crowds of people marched on the Ittihadiya presidential palace, hoisting anti-Morsi banners and holding signs equating the president to Mubarak. At the same time, thousands of Islamist Morsi supporters rallied for the president outside the Rabia al-Adawiya Mosque near the Ittihadiya palace.

More people gathered in the Mediterranean city of Alexandria, as well as the Nile Delta cities of Mansoura, Tanta and Damanhour.

At least five people were killed on Sunday in clashes between Morsi's opponents and supporters in the southern Egyptian cities of Assiut and Beni Sueif, local media reported.

Dozens of people were also injured during an attack on the Muslim Brotherhood office in Housh Eissa in the northern Nile Delta. The Brotherhood's national headquarters in a Cairo suburb also came under attack from people hurling petrol bombs and rocks and firing shotguns.

At least 400 have been injured nationwide in the past week, according to the Health Ministry, and several killed, including an American university student.

Opposition wants Morsi out

The opposition is accusing Morsi, Egypt's first freely elected president, of ignoring the goals of the revolution that toppled Mubarak, cracking down on dissent and imposing Islamist values.

Morsi has said he will not step down and that street protests cannot overrule the results of a free election. His spokesman, Ihab Fahmi, repeated calls for dialogue with the opposition, saying it is "the only framework through which we can achieve understandings."

"I cannot imagine any substitute for dialogue," Fahmi said.

The opposition protests have been driven by a group called Tamarod, Arabic for "Rebel." The group has been collecting signatures for months calling for Morsi to step down and demanding that Egypt hold new elections. On Saturday, the group claimed that 22 million people had signed their pledge.

In a show of solidarity with the Tamarod activists, at least eight members of Egypt's upper house of parliament, the Shura Council, have resigned from their positions.

"We resigned in support of 22 million Egyptians who withdrew their confidence from Morsi," Ihab al-Kharatt, an outgoing deputy, told the AFP news agency.

dr/tm (AP, Reuters, AFP, dpa)