Masked gunmen fired into crowds of protestors in Cairo's Tahrir Square before dawn Tuesday, injuring nine people. Egyptians opposed to President Mohammed Morsi have been staging a sit-in there for nearly three weeks.

They accused Morsi's Muslim Brotherhood supporters of sending trained squads to squash anti-government resistance.

Footage from a private TV station shows a Morsi supporter assuming a professional shooter stance before aiming his rifle at demonstrators.

"One of the most disturbing things was how they chanted 'Allah is Great' as they aimed at us," Mahmoud Zaghloul, a 22-year-old protestor, recalled.

Tanks and soldiers remain in place at the presidential palace.

The opposition party called on its supporters to march on the presidential place today. They want Morsi to call off Saturday's national referendum on a draft constitution.

Clashes between hundreds of thousands of Egyptians demonstrating against the president and his supporters have left at least six dead and hundreds wounded.

The demonstrators say the Islamist-dominated constitutional committee drafted a document that doesn't represent all Egyptians, subjugating women, Christians, and minorities.

Meanwhile, Morsi gave the military authority orders to assist police in arresting civilians to "maintain security for the referendum."