More than 200,000 people packed Cairo's central Tahrir Square on Tuesday evening, chanting against Egypt's Islamist president in a powerful show of strength by the opposition demanding Mohammed Morsi revoke edicts granting himself near autocratic powers.
With the mass protests in Tahrir and in several other cities - comparable in size to those during last year's uprising that overthrew autocrat Hosni Mubarak - opposition to the decrees issued last week turned into a broader outpouring of anger against the rule of Mr Morsi and his Muslim Brotherhood.
Waving Egypt's red, white and black flags, crowds of protesters marched across Cairo to stream into the iconic central plaza, birthplace of the anti-Mubarak uprising.
By the evening, it was thronging with a crowd that appeared to be more than 200,000. Clashes broke out in several cities as Morsi opponents tried to attacked offices of the Brotherhood, setting fire to at least one.
Ringing out at Tahrir was the central chant of the Arab Spring revolts: "The people want to bring down the regime," and "erhal, erhal" - Arabic for "leave, leave".
"Suddenly Morsi is issuing laws and becoming the absolute ruler, holding all powers in his hands," said protester Mona Sadek, a 31-year-old engineering graduate who wears the Islamic veil, a hallmark of piety. "Our revolt against the decrees became a protest against the Brotherhood as well."
Protest organisers on a stage in the square called for another mass rally on Friday. If the Brotherhood responds with mass rallies of its own, as some of its leaders have hinted, it would raise the prospect of greater violence after a series of clashes between the two camps in recent days.
Even as the crowds swelled in Tahrir, clashes erupted nearby between several hundred young protesters throwing stones and police firing tear gas on a street off Tahrir leading to the US embassy.
Clouds of tear gas hung close to the ground at the area. Clashes have been taking place at the site for several days, fuelled by anger over police abuses, separately from the crisis over Morsi.
A photographer working for the AP, Ahmed Gomaa, was heavily beaten by police using sticks while covering the clashes today. Police took his equipment, and Mr Gomaa was taken to hospital for treatment.