Update: Egyptian security officials say Nobel Peace laureate Mohamed ElBaradei is under house arrest. (From the AP at 8:44 a.m.)
CAIRO — Thousands of Egyptian anti-government protesters clashed Friday with police in Cairo, who fired rubber bullets into the crowds and used tear gas and water cannons to disperse them.
Police also used water cannons against Egypt's pro-democracy leader Mohamed ElBaradei and his supporters as they joined the latest wave of protests after noon prayers. Police armed with batons beat some of ElBaradei's supporters, who surrounded him to protect him.
Clusters of riot police with helmets and shields were stationed around the city, at the entrances to bridges across the Nile and other key intersections. Near the city's main Tahrir Square downtown, hundreds of riot police clustered together moved in, anticipating the arrival of thousands of protesters.
At Ramsis square in the heart of the city, thousands of protesters clashed with police as they left the al-Nur mosque after the prayers. Police used tear gas and rubber bullets. Some of the tear gas was fired inside the mosque, where women were taking refuge.
At the upscale Mohandiseen district, at least 10,000 of people were marching toward the city center chanting "down, down with Mubarak" as they demanded the ouster of President Hosni Mubarak.
Regional television stations were reporting clashes between thousands of protesters and police in several other major Egyptian cities, including the Mediterranean port city of Alexandria, Minya and Assiut south of Cairo and al-Arish in the Sinai peninsula.
In response to the threat, Egypt has apparently done what many technologists thought was unthinkable for any country with a major Internet economy: cutting itself off from the web to try and silence a protest movement taking inspiration from the ouster of Tunisia's president this month.
Mubarak, 82, has not been seen in public or heard from directly since the protests began Tuesday with tens of thousands marching in Cairo and a string of other cities. While he may still have a chance to ride out this latest challenge, his choices are limited, and all are likely to lead to a loosening of his grip on power.
The state-controlled Al-Ahram newspaper, however, sought to project a notion of normalcy, reporting on its front page that Mubarak would open the city's annual book fair on Saturday.
The government deployed an elite special operations force in Cairo on Thursday night as violence escalated outside the capital, and the Islamist Muslim Brotherhood called on its members to take to the streets after Friday afternoon prayers.
Uniformed security forces at least temporarily disappeared from the streets of central Cairo mid-morning Friday, but truckloads of riot police and armored cars started moving back about an hour later.
By late morning, thousands of black-clad riot police armed with batons and shields were deployed across the city, with the largest concentrations at Tahrir, or Liberation, Square at the heart of the city, where 10,000 protesters gathered for their first demonstration on Tuesday.
The police, backed by armored vehicles and fire engines fitted with water cannon, were also deployed in large numbers at Ramsis Square, another flashpoint in central Cairo.
The Muslim Brotherhood said at least five of its leaders and five former members of parliament had been arrested.
The group's lawyer, Abdel-Moneim Abdel-Maksoud, and spokesman, Walid Shalaby, said a large number of rank-and-file Brotherhood members also had been detained.
Egypt's four primary Internet providers - Link Egypt, Vodafone/Raya, Telecom Egypt, Etisalat Misr - all stopped moving data in and out of the country at 12:34 a.m., according to a network security firm monitoring the traffic. Telecom experts said Egyptian authorities could have engineered the cutoff with a simple change to the instructions for the companies' networking equipment.
The Internet appeared to remain cut off in Cairo but was restored in some smaller cities Friday morning. Cell-phone text and Blackberry Messenger services were all cut or operating sporadically in what appeared to be a move by authorities to disrupt the organization of demonstrations.
"We are concerned that communication services, including the Internet, social media and even this tweet, are being blocked in Egypt," State Department spokesman P. J. Crowley said on Twitter. "We continue to urge authorities to show restraint and allow peaceful protests to occur."
Egyptians outside the country were posting updates on Twitter after getting information in voice calls from people inside the country. Many urged their friends to keep up the flow of information over the phones.
A Facebook page run by protesters demanded of President Mubarak that he: declare that neither he nor his son will stand for next presidential elections; dissolve the parliament holds new elections; end to emergency laws giving police extensive powers of arrest and detention; release all prisoners including protesters and those who have been in jail for years without charge or trial; and immediately fire the interior minister.
The movement's momentum appeared to gather Thursday with the return of Nobel Peace laureate Mohamed ElBaradei and the backing of the Muslim Brotherhood.
Social networking sites were abuzz that the gatherings called after Friday prayers could attract huge numbers of protesters demanding the ouster of Mubarak. Millions gather at mosques across the city on Fridays, giving organizers a vast pool of people to tap into.
"There is a big gap between what the government says and the reality of people's lives," Nasser Shareef, a 24-year-old librarian, said as he made his way to a mosque in the upscale Mohandiseen district.
Violence escalated on Thursday at protests outside the capital. In the flashpoint city of Suez, along the strategic Suez Canal, protesters torched a fire station and looted weapons that they then turned on police. The Interior Ministry said in a statement that more than 90 police officers were injured in those clashes. There were no immediate figures on the number of injured protesters.
In the northern Sinai area of Sheik Zuweid, several hundred Bedouins and police exchanged gunfire, killing a 17-year-old. About 300 protesters surrounded a police station from rooftops of nearby buildings and fired two rocket-propelled grenades at it, damaging the walls.
The United States, Mubarak's main Western backer, has been publicly counseling reform and an end to the use of violence against protesters, signs the Egyptian leader may no longer be enjoying Washington's full backing.
In an interview broadcast live on YouTube, President Obama said the anti-government protests filling the streets show the frustrations of Egypt's citizens. "It is very important that people have mechanisms in order to express their grievances," Obama said.
On its website, the Muslim Brotherhood said it would join "with all the national Egyptian forces, the Egyptian people, so that this coming Friday will be the general day of rage for the Egyptian nation."
The Brotherhood has sought to depict itself as a force pushing for democratic change in Egypt's authoritarian system, and is trying to shed an image among critics that it aims to seize power and impose Islamic law. The group was involved in political violence for decades until it renounced violence in the 1970s.
ElBaradei, the former head of the U.N. nuclear watchdog and a leading Mubarak opponent, has sought to recreate himself as a pro-democracy campaigner in his homeland. He is viewed by some supporters as a figure capable of uniting the country's fractious opposition and providing the movement with a road map for the future.
Speaking to reporters Thursday before his departure for Cairo, ElBaradei said: "If people, in particular young people, ... want me to lead the transition, I will not let them down. My priority right now ... is to see a new regime and to see a new Egypt through peaceful transition."
Once on Egyptian soil, he struck a conciliatory note.
"We're still reaching out to the regime to work with them for the process of change. Every Egyptian doesn't want to see the country going into violence," he said.
With Mubarak out of sight, the ruling National Democratic Party said Thursday it was ready for a dialogue with the public but offered no concessions to address demands for a solution to rampant poverty, unemployment and political change.
Its comments were likely to reinforce the belief held by many protesters that Mubarak's regime is incapable, or unwilling, to introduce reforms that will meet their demands. That could give opposition parties an opening to win popular support if they close ranks and promise changes sought by the youths at the forefront of the unrest.
Mubarak has not said yet whether he will stand for another six-year term as president in elections this year. He has never appointed a deputy and is thought to be grooming his son Gamal to succeed him despite popular opposition. According to leaked U.S. memos, hereditary succession also does not meet with the approval of the powerful military.
Mubarak has seen to it that no viable alternative to him has been allowed to emerge. Constitutional amendments adopted in 2005 by the NDP-dominated parliament has made it virtually impossible for independents like ElBaradei to run for president.
This program aired on January 28, 2011. The audio for this program is not available.