Egypt's most prominent democracy advocate took up a loudspeaker and called for President Hosni Mubarak to resign, speaking to thousands of protesters who defied a curfew for a third night.
Fighter jets streaked low overhead and police returned to the capital's streets - high-profile displays of authority over a situation spiralling out of control.
Nobel Peace laureate Mohamed ElBaradei's appearance in Tahrir, or Liberation, Square underscored the jockeying for leadership of the mass protest movement that erupted seemingly out of nowhere in the past week to shake the Arab world's most populous nation.
Now in their sixth day, the protests have come to the square. Up to 10,000 protesters gathered there on Sunday, and even after the 4pm curfew, they numbered in the thousands, including families with young children, addressing Mr Mubarak with their chants of "Leave, leave, leave".
"You are the owners of this revolution. You are the future," Mr ElBaradei told the crowd after nightfall. "Our essential demand is the departure of the regime and the beginning of a new Egypt in which every Egyptian lives in virtue, freedom and dignity."
In a further sign of Mr Mubarak's teetering position after three decades in power, his top ally - the United States - called for an "orderly transition to democracy".
Asked if Washington supports Mr Mubarak as Egypt's leader, Secretary of State Hillary Clinton avoided a direct answer, telling Fox News: "We have been very clear that we want to see a transition to democracy, and we want to see the kind of steps taken that will bring that about."
German Chancellor Angela Merkel urged the Egyptian government to implement democratic reforms and stop violence against protesters.
Israeli Prime Minister Benjamin Netanyahu told his Cabinet that he was "anxiously following" the crisis, saying Israel's three-decade-old peace agreement with Egypt must be preserved.
Protesters have shrugged off Mr Mubarak's gestures of reform, including the sacking of his Cabinet and the appointment of a vice president and a new prime minister - both seen as figures from the heart of his regime.