JIM LEHRER: Late tonight, President Mubarak of Egypt appeared on television and asked for his Cabinet's resignation. That came on this fourth day of unrest.
Police battled vast crowds of protesters in Cairo and other cities. The government tried to impose an overnight curfew, and it called out the army to restore calm.
We begin our coverage with this report on today's protests from Jonathan Rugman of Independent Television News.
JONATHAN RUGMAN: Pandemonium in Egypt's capital. Riot police clashing with thousands of protesters. Years of frustration exploding on to the streets. In this, the most populous country in the Arab world, in the biggest rebellion against President Hosni Mubarak in 30 years.
"Down with the regime," they chanted, over and over, "Down with the regime."
MAN: We are fed up with the regime. This is a corrupt regime. We are fed up with the regime.
"The regime is a failure. Help us. People are (INAUDIBLE)."
JONATHAN RUGMAN: The trouble began not long after noon, Egyptians emerging from their mosques after prayers into this.
We watched a furious crowd confronting riot police, blocking the entrance to Cairo's Freedom Square. People want the regime to go, they shouted, while phalanxes of police reinforcements moved into position.
Then, the first of countless volleys of tear gas, the crowd scattering into the safety of the back streets, and more gas every time they regrouped beneath the city's concrete underpasses, and, when that didn't work, water cannons and rubber bullets.
Over the Nile, there's bright, winter sunshine, but look more closely and a crowd of thousands is streaming across, until the police forces them back, then an extraordinary calm in this rebellion: hundreds pausing for prayer before running back to the front line.
A police post was set alight, and the air has been thick with tear gas for hours, mingled with smoke from protesters' fires. And amid the screaming, the shouting and the wounded, this much is clear: Egypt's 82-year-old president has never faced anything like this.
It wasn't just Cairo. This was the port city of Suez today, where security forces lost control of the streets. Riot police were confronted by crowds in their tens of thousands. Armored vehicles and government buildings were set alight in clashes which left at least one man dead.
And walking into this firestorm is the retired U.N. diplomat who has hinted that he might be the leader of a post-Mubarak Egypt -- Mohamed ElBaradei joining protesters and calling for the regime to listen to the people, though the Nobel winner's supporters were beaten when they tried marching this afternoon.
Tonight, Cairo is in chaos. There are fires burning around the Mubarak party headquarters. The air is thick with smoke, ringing with the sound of gunfire, along with the cries of thousands calling for the end of the Mubarak regime. A nationwide block on the Internet and mobile-phone coverage has failed to stop this insurrection, and it isn't clear what will.
JIM LEHRER: It was after midnight in Cairo when President Mubarak appeared on Egyptian state television, his first appearance since the crisis began.
He said he was sorry that people had been injured. And he promised political and economic reforms. But he also defended the crackdown against protesters.
HOSNI MUBARAK, Egyptian president (through translator): There's a fine line that separates freedom and chaos. I'm absolutely on the side of freedom of each citizen in expressing our opinions. And, at the same time, I am on the side of the security of Egypt.
And I would not let anything dangerous happen that would threaten the peace and the law and the future of the country. I asked the government to submit their resignation today, and I will tell the new government starting tomorrow, in very specific goals, to work with the current situation.