Thousands of police have clashed with demonstrators for control of Cairo's Tahrir Square, leaving at least one protester dead and hundreds others injured in the Egyptian capital and prompting protests and at least one fatality elsewhere in the country.
The violence on Saturday came just nine days before Egypt's first elections since former president Hosni Mubarak was overthrown in February.
In scenes reminiscent of the 18-day uprising, protesters and police forces hurled rocks at each other, and crowds swarmed an armored police vehicle, rocking it and setting it ablaze.
At least one person was killed in Cairo, according to health officials. The AFP news agency said a 23-year-old man identified as Ahmed Mahmoud died from a bullet wound to the chest. Egyptian state television said 750 people had been injured in the clashes in Cairo.
Security officials said that protesters also rallied outside security agency headquarters in the port city of Alexandria as well as the cities of Aswan in the south and Suez on the Red Sea coast.
Media reports said at least one protester was killed in Alexandria. AFP said the man, Baha Eddin Mohamed Hussein, 25, was hit by a rubber bullet, quoting medics.
Witnesses said Cairo's violence began when riot police dismantled a small tent camp set up to commemorate protesters killed in the earlier revolt and attacked around 200 peaceful demonstrators who had camped out in the square overnight.
Tens of thousands of people had gathered in Tahrir Square on Friday to denounce Egypt's ruling military council, which has been criticised for its handling of Egypt's transition period. Protesters are angry with alleged attempts by the military to grant themselves special powers over the next elected government.
Police fired rubber bullets, tear gas and beat protesters with batons to clear the area on Saturday, said Sahar Abdel-Mohsen, an engineer who joined in the protest after a call went out on Twitter telling people to go to Tahrir Square.
Abdel-Mohsen said a friend was wounded by a rubber bullet that struck his head and that she saw another protester wounded by a pellet shot in his neck.
"Violence breeds violence," Abdel-Mohsen said. "We are tired of this and we are not leaving the square."
The number of protesters swelled to several thousand as news of the scuffles spread in the city, and thousands more riot police streamed into the square, blocking entrances and clashing with protesters.
Al Jazeera's Sherine Tadros, reporting from Cairo, said that after six hours of clashes, police had appeared to gain control of the square itself, but the violence was spreading.
"These clashes have spread to the streets and side roads coming out of Tahrir Square, and that is where all the main clashes are happening right now," she said.
Crowds chanted: "Riot police are thugs and thieves" and "Down with the Marshal," referring to Field Marshal Hussein Tantawi, Egypt's military ruler.
Activist Mona Seif, the sister of jailed blogger and activist Alaa Abd El Fattah, said Saturday's attacks on protesters were unwarranted.
"This violence is the same as the old regime," Seif said. "Police are telling us they are carrying out orders to beat us until we leave."
Al Jazeera's correspondent added: "This is the same police and state security, don't forget, that will be monitoring – or at least protecting – [upcoming] elections, standing outside the polling stations."
"So, of course, it really isn't a very good sign for things to come."
Saturday's confrontation was one of the few since the uprising to involve police forces, which have largely stayed in the background while the military takes charge of security. There was no military presence in and around the square on Saturday.
The scene was starkly different from a day earlier, when thousands of Islamists and liberals gathered to confront Egypt's military council, which promised when it took control of the country in February to restore civilian rule within six months.
Most rallies since have been led by liberal- or left-leaning groups, but Islamists dominated Tahrir Square's biggest demonstration in months, which came days before elections seen as crucial in shaping the future direction of the country.
While united against giving the army new powers, Islamists and liberals are competing for votes in the parliamentary vote, which is scheduled to begin on November 28.
The victors in that process will help choose who will draft a new constitution that will determine the character of post-revolutionary Egypt.