After days of protests that have toppled one president and shaken many others, governments across the Middle East braced on Friday for new outbursts of rage and discontent directed at entrenched regimes confronting an exceptional clamor for democracy.

The immediate epicenter of the protests was Egypt, where Internet and cellphone connections were closed or restricted in Cairo, Alexandria and other places. Riot police took to the streets of Cairo before the Friday noon prayers that in many parts of the Islamic world have been a prelude to unrest as worshippers pour onto the streets.

The protests have underscored the blistering pace of events that have transformed the visage of the Arab world, particularly among regimes that have traditionally enjoyed the support of successive administration in Washington.

Earlier this month, entrenched autocracies seemed confident of their ability to ride out protests. But, just two weeks ago, on Jan. 14, President Zine el-Abidine Ben Ali of Tunisia fled abruptly into exile after weeks of protest and his departure emboldened demonstrators to take to the streets in other countries.

The imagery of the lowly challenging the mighty has been relayed from one capital to the next, partly through the aggressive coverage of Al Jazeera, the Qatar-based satellite […]