CAIRO - The opening session of Egypt's first democratically elected Parliament in more than six decades erupted in chaos Monday as the Islamists dominating the chamber struggled to keep order and thousands of demonstrators gathered outside in an unruly mix of celebration and protest.

It took until nightfall for the Muslim Brotherhood, Egypt's mainstream Islamist group, to decisively beat back an unexpectedly vocal challenge from a dissident former member so that the parliamentarians could elect a Brotherhood stalwart, Saad el Katatni, as speaker.

Katatni's victory, by a vote of 399-97, signified an important turn in the history of the Muslim Brotherhood, which had been banned by Hosni Mubarak, the former autocratic president deposed in the Egypt revolution a year ago.

After 84 years of struggle in the shadows of monarchy and dictatorship, the Brotherhood -- a secretive, once-militant group that became the fountainhead of Islamist ideologies around the world -- was closer than ever to both political power and democratic legitimacy.

"This is democracy that had left this hall for years, and now the people have grasped it," Katatni said. "We want Egypt and the whole world to know that our revolution will continue, and we will not rest and our eyes won't sleep until the revolution fulfills all its demands."

Its triumph, in the heart of the Arab world and the center of last year's regional uprising, was the closest that Islamists have ever come to governing an Arab country.

The Brotherhood's success, however, was tempered by the noisy reminders both inside and outside of the challenges that members face in leading the country through its promised transition to democracy.

NEW YORK TIMES