The opposition protesters dubbed it a "day of departure" and prayed for an immediate end to the rule of Egyptian President Hosni Mubarak.
A cleric praised the "revolution of the young" and declared, "We want the head of the regime removed." The crowd bowed in prayer then chanted "Leave! Leave! Leave!"
U.S. officials said the Obama administration is in talks with Egyptian officials on a proposal for Egyptian President Hosni Mubarak to resign immediately, Voice of America reported. Power would be turned over to a transitional government headed by Vice President Omar Suleiman with the support of the Egyptian military.
Mubarak said Thursday that he wanted to step down, but that he feared the nation would be plunged into chaos if he did.
In an interview with ABC's Christiane Amanpour, Mubarak said the violence in the streets on Thursday between pro- and anti-government protesters troubled him. "I am fed up. After 62 years in public service, I have had enough. I want to go," Mubarak, 82, told ABC. "If I resign today, there will be chaos," he added.
The street-brawls that started Wednesday continued on Thursday, with violence increasingly aimed at journalists. More than 20 foreign journalists have been arrested.
Thousands of pro-Mubarak supporters stormed Tahrir Square on Thursday, some riding horses and camels, toward a large crowd of protesters demanding the ouster of Egypt’s leader for the past three decades.
Three Egyptians have so far been confirmed killed and at least 600 were injured in the hours-long street battles on Wednesday, which first flared just outside the gates to the country’s world famous Egyptian Museum.
The demonstration, which drew hundreds of thousands of festive pro-democracy protesters earlier in the week, degenerated into utter pandemonium with the arrival of stone-throwing pro-Mubarak demonstrators on Wednesday.
Wooden sticks, rocks and chunks of the streets — ripped up with crowbars — were tossed into crowds in both camps.
Army soldiers guarding Liberation Square have not intervened in the clashes, leaving many astonished pro-reform demonstrators questioning earlier pledges by the military to protect Egyptian citizens.
Fires burned throughout the night on Wednesday, after cars were lit ablaze by homemade Molotov cocktails.
Several pro-Mubarak demonstrators climbed apartment buildings near Tahrir Square, tossing glass soda bottles filled with gasoline into the crowds below.
Scores of gunshots were fired during the melee into the early hours of Thursday.
In perhaps the most bizarre spectacle of the day on Wednesday, a small cavalry of pro-Mubarak horsemen and one camel driver charged the opposing side, lashing unarmed pro-reformers with whips and wooden canes.
The clashes come one day after one of the largest pro-reform demonstrations in Egypt’s recent history, and a late-night televised speech by Mubarak promising he would not run for re-election at the end of his term in September.
U.S. President Barack Obama strongly condemned Wednesday’s attack through spokesman Robert Gibbs, who added that the transition of leadership in Egypt should begin sooner than September.
"An orderly transition [of power] must be meaningful, it must be peaceful and it must begin now," said Obama in a speech on Feb. 1.
Egypt is one of America’s closest allies in the Middle East, in part because of the country’s 1979 peace treaty with Israel. The Arab world’s most populous nation has been rocked by an unprecedented series of protests in the past nine days, posing one of the first serious challenges to Mubarak’s government in his three decades of rule.
A defiant Mubarak has made surprising concessions this week — from sacking his cabinet to the naming of a vice president — in order to quell the growing unrest.
Nothing, however, has so far convinced Egypt’s pro-democracy demonstrators to relent.
“[Mubarak] will leave. Or we will stay,” chanted rock-dodging protesters on Wednesday.
The violence, though, left many Egyptians wondering whether brute force was the last draw performed by a president with dwindling options.
Backers of Mubarak arrived on the scene in coordinated patterns, grouped into tightly-packed microbuses and with weapons on the ready, said pro-democracy protesters, raising accusations that clashes may have been instigated by government security forces themselves.
Egypt’s Ministry of Interior was quick to deny that members of state security were involved.
Plainclothes security forces, however, have been used before to quash political demonstrations and opposition rallies during elections in Egypt, which are frequently marred by allegations of official intimidation.