Anti-government demonstrators clashed with security forces facing Egypt's presidential palace Friday evening, throwing petrol bombs as police responded with tear gas and water cannons.
Huge balls of fire were seen on the sides of palace as smoke billowed over the streets.
Opposition protests had grown larger by late afternoon in Cairo as groups of demonstrators gathered in Tahrir Square and near the palace. Cold weather and intermittent rain may have discouraged many people from turning out earlier but crowds swelled by nightfall.
Arab media reported that Egyptian Army troops were stationed at the entrances of Cairo to maintain security. A heavy security detail was near the presidential palace.
Opposition figures have called on Egyptian President Mohamed Morsi to form a national unity government that grants them seats in the Cabinet.
Mr. Morsi's allies have resisted that demand, saying the opposition is trying to gain power that it could not win through elections.
On Thursday, Egypt's Islamist and liberal politicians agreed to renounce violence and join a national dialogue aimed at resolving the country's deadliest unrest in months.
Egyptian Islamic scholar Sheik Ahmed al-Tayeb chaired Thursday's meeting at the Cairo headquarters of Sunni Islam's highest seat of learning, al-Azhar. He told the representatives of the country's feuding political factions that the "only way" to solve their differences is through an inclusive dialogue.
Senior members of the Muslim Brotherhood movement that helped President Morsi sweep into power in an election last year attended the meeting.
They sat opposite prominent liberal figures such as former U.N. nuclear agency chief Mohamed ElBaradei and former Arab League chief Amr Moussa. Other participants included Egyptian youth activists and church leaders.
ElBaradei said he came out of the talks with a feeling of "optimism." He promised to do whatever he can to promote goodwill and build trust between the factions.
Delegates signed a document renouncing violent forms of protest and calling for the creation of a committee to arrange further talks as part of a national dialogue proposed by Mr. Morsi.
It is not clear whether the pledges will prevent more confrontations on the streets.
In the past week, nearly 60 people were killed in anti-government street protests in several cities, mostly along the Suez Canal.