Huge protests calling for the resignation of Egypt’s President Mohammed Morsi and early presidential elections are taking place in the capital, Cairo, and other cities.
Tens of thousands of opponents have massed in Tahrir Square and outside the main presidential palace.
One man died when rival groups clashed in a city south of the capital.
In Cairo, stones and petrol bombs were thrown at the headquarters of the ruling Muslim Brotherhood.
Protest leaders have called on demonstrators to stay on the streets until Mr Morsi resigns.
They accuse the country’s first Islamist president of failing to tackle economic and security problems since taking power a year ago.
A presidential spokesman urged the protesters to respect the democratic process while Morsi supporters massed in the Cairo suburb of Nasr City.
Demonstrations are being reported across the country:
- In Alexandria, the second-biggest city, thousands of protesters gathered for a march to the central Sidi Gaber area, BBC Arabic’s Rami Gabr reports
- A big stage has been erected in the main square of the Suez Canal city of Port Said, and protesters are checking the identities of those going in and out of the square, BBC Arabic’s Attia Nabil reports
- Rallies were also expected in Suez, Monofia and Sharqiya – the birthplace of President Morsi.
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 Cairo, anti-government protesters attacked the Muslim Brotherhood headquarters, which had been fortified with sandbags earlier. Staff inside said they had not broken in, Reuters news agency reports.
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.
He told reporters that the presidency was open to a “real and serious national dialogue”.
As darkness fell, the opposition National Salvation Front 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 National Salvation Front is among the 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.
The BBC’s Aleem Maqbool in Cairo says many ordinary Egyptians – angered by Mr Morsi’s political and economic policies – are taking part in the rally in Tahrir Square.
Hanan Bakr, who travelled specially from Dubai where she lives, to join the “second Egyptian revolution”, told the BBC: “I’m hoping to stay on the streets until the whole regime of the Brotherhood is brought down.
“If Egypt falls under Islamist extremism, this will affect the whole region.”
Mr Morsi, who hails from the Muslim Brotherhood, became Egypt’s first Islamist president on 30 June 2012, after winning an election considered free and fair.
His first year as president has been marred by constant political unrest and a sinking economy.