Hundreds of anti-government protesters returned Saturday to the battered streets of central Cairo, shouting for Hosni Mubarak to step down and attacking police even as the Cabinet resigned on the orders of the Egyptian president.

The sight of protesters pouring into Cairo's downtown Tahrir Square and clashing with police for a fifth day indicated Mubarak's pledges of reform and the dismissal of the government had done little to cool the anger over Egypt's crushing poverty, unemployment and corruption. In a nationally televised speech after midnight, Mubarak refused to meet the protesters' ultimate demand _ for him to step down.

Over five days of protests _ the largest Egypt has experienced in decades _ crowds have overwhelmed police forces in Cairo and other cities around the nation with their numbers and in attacks with rocks and firebombs.

Overnight, the government called in military forces and by morning the army had replaced police in guarding government buildings and other key areas around the capital.

Several tanks were parked in the vast Tahrir Square, but soldiers did not intervene in Saturday's protest there. Protesters hurling stones attacked riot police trying to enter the square, and officers responded with a barrage of tear gas and rubber bullets.

"What we want is for Mubarak to leave, not just his government," said Mohammed Mahmoud. "We will not stop protesting until he goes."

Some protesters were wearing T-shirts with "Down with Mubarak" emblazoned on their fronts. Others chanted "The people want to topple the regime."

Not far from the square, the army sealed off the road leading to the parliament and Cabinet buildings. Though the military has yet to intervene in the clashes, state television quoted army officials as calling on people not to gather and protest, saying violators would be subject to the law.

Along the Nile, smoke was still billowing from the ruling party's headquarters, which protesters set ablaze during Friday's unrest, the most dramatic day of protests since the unrest began on Tuesday.

Also Saturday, mobile phone services were restored after a government-ordered communications blackout aimed at stopping Friday's protests. Protesters have used text messaging and social networking websites to coordinate demonstrations.

Vodafone and Mobinil cell phone services were working Saturday morning, about 24 hours after they were cut, but Internet service appeared to remain blocked.

A week of unrest has killed at least 25 protesters and 10 policemen, security officials said on Saturday.

They said the death toll was likely to significantly rise as more reports come in from hospitals and morgues around the country. They also said that at least 750 policemen and 1,500 protesters have been wounded in clashes.

The officials were speaking on condition of anonymity because they were not authorized to share the information with the media.

Mubarak, confronted with the most dire threat to his three decades of authoritarian rule, faced his nation for the first time since the unrest began. In a televised address at midnight, he made vague promises of social reform in what is likely to be interpreted as an attempt to cling to power rather than a genuine pledge solve Egypt's pressing problems.

He also defended his security forces and accused the protesters of plotting to destabilize Egypt and destroy the legitimacy of his regime, outraging those still in the streets well into the night.

"We want Mubarak to go and instead he is digging in further," protester Kamal Mohammad said. "He thinks it is calming down the situation but he is just angering people more."

Mubarak's speech came after a tumultuous day in which protesters burned down and looted the headquarters of Mubarak's political party along the banks of the Nile and set fire to many other buildings, roaming the streets of downtown Cairo in defiance of a night curfew enforced by the army. There was also widespread looting of supermarkets, shopping malls, casinos and offices of cell phone companies.

The security officials said protesters burned down police stations throughout Cairo, stealing firearms and ammunition and setting some jailed suspects free. They also burned dozens of police trucks in Cairo, Alexandria and Suez.

The officials also reported widespread looting in Cairo of supermarkets, shopping malls and offices of cell phone companies.

Zahi Hawass, Egypt's top archaeologist, meanwhile, told state television on Saturday that he was "seriously concerned" about the safety of the capital's famed Egyptian Museum. He said next door buildings gutted by fires on Friday night were likely to collapse and damage the museum, home to the treasures of king Tutankamun and other priceless artifacts.

By daybreak, several of the city's main streets were strewn with rocks and burned-out police vehicles even as some vehicle and foot traffic returned to the center of the city.

Buildings, statues and even armored security vehicles were covered in anti-Mubarak graffiti, including the words "Mubarak must fall," which by morning had been written over to say "Mubarak fell."

A heavy police crackdown and other extreme measures by the government _ including the shutting down of all Internet and mobile phone services in Cairo and other areas on Friday _ did not stop the surging crowds. With police beaten back in many places, the government called the army into the streets and imposed a nationwide dusk-to-dawn curfew.

Egypt's crackdown drew harsh criticism from the Obama administration and even a threat Friday to reduce a $1.5 billion foreign aid program if Washington's most important Arab ally escalates the use of force.

Stepping up the pressure, President Barack Obama told a news conference he called Mubarak immediately after his TV address and urged the Egyptian leader to take "concrete steps" to expand rights and refrain from violence against protesters.

"The United States will continue to stand up for the rights of the Egyptian people and work with their government in pursuit of a future that is more just, more free and more hopeful," Obama said.

Throughout Friday, flames rose in cities across Egypt, including Alexandria, Suez, Assiut and Port Said, and security officials said there were protests in 11 of the country's 28 provinces.

Calling the anti-government protests "part of a bigger plot to shake the stability and destroy legitimacy" of Egypt's political system, a somber-looking Mubarak said: "We aspire for more democracy, more effort to combat unemployment and poverty and combat corruption."

He was expected to name a new Cabinet on Saturday.

His promises fell short of the protesters' demands for him to step down.

At least one protester was killed Friday, bringing the toll for the week to eight. Demonstrators were seen dragging bloodied, unconsciousness protesters to waiting cars and on to hospitals, but no official number of wounded was announced.

Nobel Peace laureate Mohamed ElBaradei, a leading pro-democracy advocate, was soaked with a water cannon and briefly trapped inside a mosque after joining the protests. He was later placed under house arrest.

In the capital on Friday night, hundreds of young men carted away televisions, fans and stereo equipment looted from the ruling National Democratic Party, near the Egyptian Museum. Young men formed a human barricade in front of the museum to protect one of Egypt's most important tourist attractions.

Others around the city looted banks, smashed cars, tore down street signs and pelted armored riot police vehicles with paving stones torn from roadways.

"We are the ones who will bring change," declared 21-year-old Ahmed Sharif. "If we do nothing, things will get worse. Change must come!" he screamed through a surgical mask he wore to ward off the tear gas.

Egypt's national airline halted flights for at least 12 hours and a Cairo Airport official said some international airlines had canceled flights to the capital, at least overnight. There were long lines at many supermarkets and employees limited bread sales to 10 rolls per person.

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Ben Curtis and Diaa Hadid contributed to this report.