Egypt headed for another round of slugfest between largely secular opposition groups and Islamists backing President Muhammed Mursi, with massive rival rallies held on Tuesday, even as the powerful army called for dialogue to end the crisis in the polarised nation.
Tens of thousands of protesters filled the streets in the Egyptian capital to demonstrate for and against a December 15 referendum on a new Islamist constitution.
Earlier, on the day which many people believe will be decisive in the current political crisis in Egypt, at least 10 protesters were injured in an armed attack at Tahrir Square, where an open-ended sit-in has been staged since November 23. Unknown attackers fired birdshots at protesters in the square.
Nine people suffered injuries to their arms and legs, while one protester suffered a head injury, a health ministry official said.
The attack caused a wave of chaos in the square, with protesters chanting "the people want the fall of the regime" in response, before calm eventually returned.
Hundreds of Egyptian protesters breached a concrete and metal barricade outside the presidential palace and forced back the soldiers manning it.
The protesters pulled apart a high metal gate bar by bar and toppled concrete blocks with chains. Soldiers had erected the barrier to block access roads following deadly clashes last week. The soldiers fell back closer to the palace.
Six tanks were stationed close to the walled compound.
Security across the capital was tightened and police deployed anti-riot vehicles in central Cairo after the firing on Tuesday.
Meanwhile, General Abdel Fattah al-Sissi, the country's armed forces chief and defence minister, made an appeal to all political groups and movements "for the sake of Egypt" to meet on Wednesday at a Cairo military sports complex, according to a statement.
Mursi amended a law so that voters cannot cast their ballots outside their electoral districts, as they had in the past. Being able to vote anywhere had been a convenience, a presidential statement said, but it creates a burden on electoral officials.
Earlier, the government granted the military the power to make arrests during the electoral period, a power previously limited to police.
The move is designed to secure the voting process and will be rolled back once the election results are published, presidential spokesman Yasser Ali said.
The present political turmoil began after President Mursi granted himself absolute powers through the November 22 decree that had put his decisions beyond judicial review, a move which gained him titles like "dictator" and "Pharaoh".
Mursi tried to calm protests by annulling the decree, but decided to go ahead with the December 15 referendum on a new constitution as scheduled.
Egypt's Constituent Assembly on November 30 in a marathon session approved a draft constitution imposing Islamic values, a move opposed by Liberals as an attempt to restrict freedom of speech and religion in the country.
According to Egyptian state TV, the articles passed, stipulated that Islam is the religion of the state, and the principles of Sharia, or Islamic law, are the "main source of legislation".
Opposition parties rejected the referendum and called for massive march towards presidential palace to protest it.
Islamist groups were also holding rival counter demonstrations, raising fears of further bloody clashes on the streets of the Egyptian capital.
So far, seven people have been killed in clashes between the Islamist Muslim Brotherhood and opposition supporters who are also besieging Mursi's presidential palace.
The military has warned of "disastrous consequences" if the political crisis gripping the country was not resolved through dialogue and urged all political forces to pursue dialogue.