CAIRO - The Egyptian capital descended into near-anarchy Friday night, as the government sent riot police, and then the army, to quell protests by tens of thousands of demonstrators determined to push President Hosni Mubarak from office.

By the end of the day-long battle, the protesters were still standing and the police were nowhere to be seen. Mubarak - who had not spoken publicly since the protests began Tuesday - made a televised speech after midnight, announcing that he had asked his cabinet to resign. The move fell far short of protesters' demands and seemed likely to ensure that the anti-government demonstrations that have erupted here would continue.

President Obama said a short time later that he had talked with the Egyptian president after his speech and pressed Mubarak to make long-promised reforms. "What is needed are concrete steps to advance the rights of the Egyptian people," Obama said.

It remained unclear late Friday what role the Egyptian military might play. Mubarak, a former air force officer, draws much of his strength from the military, and any decision by the armed forces to withdraw support would mean the certain end of his rule.

But unlike the police, which unleashed an arsenal of weapons against the demonstrators, the military did not take any immediate action, and protesters gleefully welcomed the soldiers' arrival in a thundering of personnel carriers.

Protesters were honking their horns in celebration and roaming freely through central parts of the city late in the evening, in defiance of a strict curfew. The night air was thick with black smoke, and the sounds of explosions, gunshots, sirens, cries and occasional cheers echoed through the darkness.

The protests, which were launched in cities nationwide but were largest in Cairo, were the most serious in Egypt's modern history. Protesters have called for Mubarak, who at 82 has ruled this country with an iron fist for 30 years, to give up his position, leave the country and allow fresh elections.

Success in ousting Mubarak would be a remarkable achievement for a group of demonstrators who have no charismatic leaders, little organization, and few clear objectives beyond removing this nation's autocratic president and other members of his ruling clique.

Before this week, few thought a mass anti-government movement was possible in Egypt, a country that has little experience with democracy. But after Friday's protests, the campaign to oust Mubarak only seems to be gathering strength.

Egyptian demonstrators are hoping to replicate the success of pro-democracy advocates in Tunisia, who this month ousted their autocratic president and sparked a wave of imitators across the region. Because Egypt has long been seen as the political center of the Arab world, the end of Mubarak's rule would reverberate particularly deeply.

The government had worked assiduously to keep the protests from even happening. It took extraordinary measures to block communications, cutting all Internet connections and mobile phone networks. Overnight Thursday, dozens of opposition leaders were rounded up and arrested. At dawn Friday, thousands of riot police filled the streets of Cairo.

Mohamed ElBaradei, a political reform advocate and Nobel Peace Prize laureate who returned to Egypt from abroad to participate, was soaked with a water cannon and later placed under house arrest, the Associated Press reported. ElBaradei, the former chief of the International Atomic Energy Agency, has said he wants to lead Egypt in a peaceful transition to democratic government.