Huge protests across Egypt calling for the resignation of President Mohammed Morsi have taken place through the night, with some outbreaks of violence.
In the capital, Cairo, tens of thousands of people massed in Tahrir Square and outside the presidential palace in the biggest demonstration there since the 2011 revolution.
At least one person was killed in clashes at Cairo's headquarters of Mr Morsi's Muslim Brotherhood movement.
Four others died in clashes elsewhere.
Millions of protesters across the country accuse the country's first Islamist president of failing to tackle economic and security problems since taking power a year ago.
The demonstration was largely peaceful, but some protesters later threw stones and petrol bombs at the Cairo headquarters of the Muslim Brotherhood.
At least one person was killed when shooting broke out near the political office, activists and a hospital official said.
Meanwhile, thousands of Mr Morsi supporters staged a rally in the Cairo suburb of Nasr City.
A presidential spokesman later urged the protesters to respect the democratic process, referring to Mr Morsi's victory in last year's elections which were widely seen as free and fair.
One clear achievement of President Morsi's opponents has been to get so many people out on to the streets, BBC's Middle East editor Jeremy Bowen reports from Cairo.
The last time such numbers were seen on the square was during the revolution in 2011 which saw the removal of President Hosni Mubarak from power.
The question they face now is how to fashion a political strategy that can rival the organisation of the Muslim Brotherhood, he says.
Another big question, he adds, is what the army will do. The defence minister has warned that the military may intervene if Egypt becomes ungovernable.
On Sunday, one man was killed and at least 24 injured in Beni Suef, 115km (71 miles) south of Cairo, security sources said.
According to a report on the Ahram news website, Morsi supporters attacked an opposition rally and unidentified gunmen opened fire. The report could not be confirmed independently.
In the southern city of Assiut, three people died and several were injured when shots were fired at protesters, reportedly by attackers on a motorcycle.
According to the health ministry, 253 people were injured across the country during Sunday's protests.
In Cairo, unidentified persons attacked the Muslim Brotherhood headquarters, which had been fortified with sandbags earlier. Staff inside said they had not broken in, Reuters news agency reports.
Demonstrations were also held in Alexandria, Port Said, Suez and other cities.
Presidential spokesman Ihab Fahmi called on all Egyptians to "unite and listen to the sound of wisdom".
"Political diversity necessitates on all parties to abide by the democratic process," he said.
And he reiterated that President Morsi was open to a "real and serious national dialogue".
As darkness fell, the opposition National Salvation Front (NSF) released what it called "Revolution Statement 1", calling on protesters across Egypt to "maintain their peaceful [rallies] in all the squares and streets and villages and hamlets of the country... until the last of this dictatorial regime falls".
The NSF is among liberal and secular opposition groups which have endorsed a petition organised by the grassroots movement Tamarod (Rebellion), which calls for a snap election. Opposition activists say more than 22 million people have signed it.
There was also some evidence of anti-American and anti-Israeli feeling among the protesters, with one flag portraying President Morsi inside a Star of David.
The BBC's Aleem Maqbool in Cairo says many ordinary Egyptians - angered by Mr Morsi's political and economic policies - have been taking part in the rally in Tahrir Square.
At one point, army helicopters flew over Tahrir Square and dropped Egyptian flags, to cheers from the anti-Morsi crowd, he says.
Mr Morsi, who hails from the Muslim Brotherhood, became president on 30 June 2012.
His first year as president has been marred by constant political unrest and a sinking economy.