The Qatar-based network has given nearly round-the-clock coverage to the unprecedented uprising against Egyptian President Hosni Mubarak and had faced criticism by some government supporters and other Arab leaders as a forum to inspire more unrest.

Al-Jazeera’s flagship Arabic channel has faced numerous bans and backlash across the Arab world, including bitter complaints this month from the Palestinian Authority over allegations that its reporting favored rival Hamas over leaked documents about peace talks with Israel. Al-Jazeera also broadcasts in English.

But the ban by Egyptian officials comes amid one of the most pivotal Arab political showdowns in decades and a possible watershed moment for Arab networks expanding their presence on the web and social media. The blanket coverage offers another example of how border-spanning outlets such as Al-Jazeera and the worldwide reach of the Internet have destroyed the once-unchallenged control of media by governments.

Al-Jazeera called the Egyptian ban "an act designed to stifle and repress the freedom of reporting by the network and its journalists."

"In this time of deep turmoil and unrest in Egyptian society, it is imperative that voices from all sides be heard," said the statement from its headquarters in Qatar’s capital Doha. "The closing of our bureau by the Egyptian government is aimed at censoring and silencing the voices of the Egyptian people."

The network promised to continue its coverage, but it was unclear in what form. It said Al-Jazeera journalists would provide updates on Twitter. The network had previously posted clips from broadcasts on YouTube.

The station broadcast video clips tagged as "live" showing crowds in Cairo’s central Tahrir Square, but they appeared to be from fixed rooftop cameras and were not accompanied by reports directly from Egypt. It was unclear how Egypt’s ban would affect such shots; the view from the fixed camera continued after night fell in Cairo.

Al-Jazeera said the government shut off the channel’s signal from an Egyptian satellite. Egyptians with satellite dishes could adjust them to point to other satellites beaming the Al-Jazeera signal, but that is not easy to do. In recent days, the channel gave viewers the coordinates to make the change.

It also was not immediately clear whether Egypt’s ban would extend to other Arab broadcasters, such as Dubai-based Al-Arabiya.

In contrast, at least one Egyptian state TV channel late Saturday and early Sunday started broadcasting soothing pharaonic pictures, shots of the tranquil Nile River and greenery after ending a newscast in which they listed the areas where thugs were active in Cairo.

"The shutting down of Al-Jazeera is a brazen violation of the fundamental right of Egyptians to receive information as their country is in turmoil," said Mohamed Abdel Dayem, Middle East and North Africa program coordinator for the Committee to Protect Journalists. "The international community should prevail upon President Mubarak to lift this censorship immediately."

Egypt has moved aggressively to try to control cell phones and the web since protests swelled late last week, inspired by the uprising in Tunisia that drove its long-ruling leader from power. Egyptian authorities cut cell phones and web links in tactics that mirrored the information choke-hold imposed by Iran’s security forces in the chaos after last year’s disputed elections.

Anti-government riots also have spread to Yemen, where President Ali Abdullah Saleh said the tone of Al-Jazeera’s coverage incited "unrest, violence and sabotage in the Arab countries."

Al-Jazeera has been frequently at odds with authorities in the Middle East, previously facing bans or restrictions in Saudi Arabia and Iraq. In December, its offices where closed in Kuwait after it broadcast a clash between security forces and opposition groups.

The Qatari government bankrolled Al-Jazeera when it launched in 1996 and is believed to still fund the station, but it operates with considerable editorial freedom compared with other government-run media outlets in the Arab world.

The network is part of a wider effort by Qatar’s emir, Sheik Hamad bin Khalifa Al Thani, to widen the Gulf nation’s political and cultural reach. Qatar has taken a lead on several difficult regional issues, including peace talks for Sudan’s Darfur region, and was selected to host the 2022 World Cup.

But some media observers note that Al-Jazeera’s enthusiastic coverage of the protesters leave it exposed to questions about its leanings.

"Al-Jazeera actually spun these protests as noble efforts worthy of international support and duplication," said Philip Howard, a University of Washington professor who follows media trends in the Muslim world. "I think their coverage of every dictator with 30-plus years of rule has been consistently unflattering."

On Al-Jazeera’s homepage, comments about the reporting ban by Egypt spanned from outrage to quips that Al-Jazeera got what it deserved.

"We need 100 Al-Jazeeras to expose the practices of government," wrote one post without giving a home country.

Another from Egypt attacked Al-Jazeera and asked: "Do you want to control the decisions of the nations? You criticize Kuwait, Morocco, Egypt and other Arab countries except Qatar."

Some of the harshest comments recently against Al-Jazeera have come from supporters of Palestinian President Mahmoud Abbas, who claim that leaked documents about Middle East peace talks sought to undercut Abbas and favor his rival Hamas.

In pro-Abbas marches in the West Bank last week, some raised homemade Israeli flags with the Star of David replaced by the Al-Jazeera logo. Others chanted "Jazeera, Mossad" — claiming that Al-Jazeera was playing into Israel’s hands by trying to weaken Abbas.

Nashat Aqtash, media professor at the West Bank’s Bir Zeit University, called Al-Jazeera a "very lucrative political investment" for tiny Qatar.

"Al-Jazeera might have a political agenda, but it tackled the most sensitive issues for the Arab world and became No. 1 simply because we lack media in the Arab world," Aqtash said. "Media in the Arab world is still mostly government- and partisan-driven media, not sources of information."

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Associated Press writer Mohammed Daraghmeh in Ramallah, West Bank, contributed to this report.