Demonstrators rejected a call from Egypt's Islamist President Mohammed Mursi for a national dialogue after deadly clashes around his palace.
They demanded the "downfall of the regime" - the chant that brought down Hosni Mubarak.
Mr Mursi said in a televised speech late tonight that plans were on track for a referendum on a new constitution on 15 December despite clashes that killed seven people.
He proposed a meeting on Saturday with political leaders, "revolutionary youth" and legal figures to discuss the way forward after that.
But a leading activist group rejected the offer, and fresh demonstrations were called for tomorrow.
The April 6 movement, which played a prominent role in igniting the revolt against Mr Mubarak, said on its Facebook page that tomorrow's protests would deliver a "red card" to Mr Mursi.
Egypt has been in turmoil since Mr Mursi issued a decree on 22 November awarding himself wide powers and shielding his decisions from judicial review.
His Islamist supporters say the decree was necessary to prevent Mubarak-era judges from interfering with reforms.
A constitution drawn up by a body dominated by Islamists is due to be put to a referendum next week.
The opposition has demanded that Mr Mursi scrap his decree, postpone the referendum and redraft the constitution.
In his address, Mr Mursi said: "I call for a full, productive dialogue with all figures and heads of parties, revolutionary youth and senior legal figures to meet this Saturday."
Several thousand opposition protesters near the palace waved their shoes in derision after his speech and shouted "Killer, killer" and "We won't go, he will go" - another of the slogans used against Mr Mubarak in last year's revolt.
The Cairo headquarters of the Muslim Brotherhood, the group that propelled Mr Mursi to victory in a June election, was set ablaze. Other offices of its political party were attacked.
Mr Mursi said his entire decree would lapse after the constitutional referendum, regardless of its result.
He said a new constituent assembly would be formed to redraft the constitution if Egyptians rejected the one written in the past six months.
The Republican Guard, an elite unit whose duties include protecting the presidential palace, restored peace tonight after a night of violence outside the palace, ordering rival demonstrators to leave by mid-afternoon.
Mr Mursi’s supporters withdrew, but opposition protesters remained, kept away by a barbed wire barricade guarded by tanks.
By evening their numbers had swelled to several thousand.
Thousands of supporters and opponents of Mr Mursi had fought well into the early hours of this morning, using rocks, petrol bombs and guns.
Officials said 350 were wounded in the violence.
Six of the dead were Mr Mursi supporters, the Muslim Brotherhood said.
Opposition groups have called for protests after Friday prayers aimed at "the downfall of the militia regime", a dig at what they see as the Brotherhood's organised street muscle.
A communique from a leftist group urged protesters to gather at mosques and squares across Egypt, and to stage marches in Cairo and its sister city Giza, converging on the presidential palace.
"Egyptian blood is a red line," the communique said.
Hardline Islamist Salafis also summoned their supporters to protest against what they consider biased coverage of the crisis by some private Egyptian satellite television channels.
Since Mr Mursi issued his decree, six of his advisers have resigned.
Essam al-Amir, the director of state television, quit today, as did a Christian official at the presidency.
The Brotherhood's supreme guide, Mohamed Badie, called for unity, saying divisions "only serve the nation's enemies".
The Islamists, who have won presidential and parliamentary elections since Mr Mubarak was overthrown, are confident they can win the referendum and the parliamentary election to follow.