CAIRO — Cries of "Egypt is free" rang out and fireworks lit up the sky over Cairo’s Tahrir Square where hundreds of thousands danced, wept and prayed in joyful pandemonium Friday after 18 days of mass pro-democracy protests forced President Hosni Mubarak to hand over power to the military, ending three decades of authoritarian rule.

Ecstatic protesters hoisted soldiers onto their shoulders and families posed for pictures in front of tanks in streets flooded with residents of the capital of 18 million people streaming out to celebrate. Strangers hugged strangers, some fell to kiss the ground, and others stood stunned in disbelief. Chants of "Hold your heads high, you’re Egyptian" roared with each burst of fireworks overhead.

"I’m 21 years old and this is the first time in my life I feel free," an ebullient Abdul-Rahman Ayyash, born eight years after Mubarak came to power, said as he hugged fellow protesters in Tahrir, or Liberation, Square.

The military, which effectively carried out a coup at the pleas of protesters that it push Mubarak out, announced on state television that is was committed to shepherding demands for greater democracy and that it would announce the next steps soon, possibly including the dissolving of parliament and creation of a transitional government to lead reforms.

Mubarak’s downfall at the hands of the biggest popular uprising in the modern history of the Arab world had stunning implications for the United States and the West, Israel, and the region, unsettling authoritarian rulers across the Mideast.

The 82-year-old leader was the epitome of the implicit deal the United States was locked into in the Middle East for decades: Support for autocratic leaders in return for their guarantee of stability, a bulwark against Islamic militants and peace — or at least an effort at peace — with Israel.

The question for Washington now was whether that same arrangement will hold as the Arab world’s most populous state makes a potentially rocky transition to democracy, with no guarantee of the results.

At the White House, President Barack Obama said "Egyptians have inspired us" and said of the important questions that lay ahead, "I’m confident the people of Egypt can find the answers."

The United States at times seemed overwhelmed throughout the 18 days of upheaval, fumbling to juggle its advocacy of democracy and the right to protest, its loyalty to longtime ally Mubarak and its fears the fundamentalist Muslim Brotherhood — or more radical groups — could gain a foothold. His fall came 32 years to the day after the collapse of the shah’s government in Iran — the prime example of a revolution that turned to Islamic militancy.

Washington’s concerns frustrated the young protesters, who argued that while the powerful Brotherhood would have to play a future political role, its popularity would be diminished in an open system where other ideologies were freed to outweigh it.

Neighboring Israel watched with the crisis with unease, worried that their 1979 peace treaty could be in danger. It quickly demanded on Friday that post-Mubarak Egypt continue to adhere to it.

Any break seems unlikely in the near term: The military leadership supports the treaty. Anti-Israeli feeling is strong among Egyptians, and a more democratic government may take a tougher line toward Israel in the chronically broken-down peace process. But few call for outright abrogating a treaty that has kept peace after three wars in the past half-century.

From the oil-rich Gulf states in the east to Morocco in the west, regimes both pro- and anti-U.S. could not help but worry they could see a similar upheaval. Several of the region’s authoritarian rulers have made pre-emptive gestures of democratic reform to avert their own protest movements.

The lesson many took: If it could happen in only three weeks in Egypt, where Mubarak’s lock on power had appeared unshakable, it could happen anywhere. Only a month earlier, Tunisia’s president was forced to step down in the face of protests.

Perhaps more surprising was the genesis of the force that overthrew Mubarak. The protests were started by a small core of secular, liberal youth activists organizing on the Internet who only a few months earlier struggled to gather more than 100 demonstrators at a time. But their work through Facebook and other social network sites over the past few years built a greater awareness and bitterness among Egyptians over issues like police abuse and corruption.

When the called the first major protest, on Jan. 25, they tapped into a public inspired by Tunisia’s revolt and thousands turned out, beyond even the organizers’ expectations. From there, protests swelled, drawing hundreds of thousands. The Muslim Brotherhood joined in. But far from hijacking the protests as many feared, it often seemed co-opted by the protesters, forced to set aside its hard-line ideology at least for now to adhere to democratic demands.

About 300 people were killed in the course of the turmoil. Police attacked the first protests with water cannons and gunfire and then a force of regime supporters —believed to be paid thugs — assaulted Tahrir trying to dislodge the protesters, only to be beaten back in two days of pitched battles.

Wael Ghonim, a Google Inc. executive who earlier this year secretly opened one of the Facebook pages that became an organizing forum for the protests, said he "went mad’ when he heard the news of Mubarak’s ouster.

"I don’t want to become of the face of this revolution … I did my best," he told The Associated Press. "I expect a bright future. I trust in 80 million Egyptians."

Mubarak, a former air force commander came to power after the 1981 assassination of his predecessor Anwar Sadat by Islamic radicals. Throughout his rule, he showed a near obsession with stability, using rigged elections and a hated police force accused of widespread torture to ensure his control.

He resisted calls for reform even as public bitterness grew over corruption, deteriorating infrastructure and rampant poverty in a country where 40 percent live below or near the poverty line.

Up to the last hours, Mubarak sought to cling to power, handing some of his authorities to Suleiman while keeping his title.

But an explosion of protests Friday rejecting the move appeared to have pushed the military into forcing him out completely. Hundreds of thousands marched throughout the day in cities across the country as soldiers stood by, besieging his palaces in Cairo and Alexandria and the state TV building. A governor of a southern province was forced to flee to safety in the face of protests there.

Mubarak himself flew to his isolated palace in the Red Sea resort of Sharm el-Sheikh, 250 miles from the turmoil in Cairo.

Vice President Suleiman — who appears to have lost his post as well in the military takeover — appeared grim as he delivered the short announcement.

"In these grave circumstances that the country is passing through, President Hosni Mubarak has decided to leave his position as president of the republic," he said. "He has mandated the Armed Forces Supreme Council to run the state. God is our protector and succor."

Nobel Peace laureate Mohammed ElBaradei, whose young supporters were among the organizers of the protest movement, told The Associated Press, "This is the greatest day of my life."

"The country has been liberated after decades of repression," he said adding that he expects a "beautiful" transition of power.

The question now turned to what happens next. Protesters on Friday had overtly pleaded for the army to oust Mubarak. The country is now ruled by the Armed Forces Supreme Council, the military’s top body consisting of its highest ranking generals and headed by Defense Minister Field Marshal Hussein Tantawi.

After Mubarak’s resignation, a military spokesman appeared on state TV and promised the army would not act as a substitute for a government based on the "legitimacy of the people."

He said the military was preparing the next steps needed "to acheive the ambitions of our great nation" and would announce them soon. He praised Mubarak for his contributions to the country. Pointedly he did not salute his former commander-in-chief. Instead he stood at attention and raised his hand to his cap in a salute to protesters killed in teh unrest.

Earlier in the day, the council vowed to guide the country to greater democracy. It said was committed "to shepherding the legitimate demands of the people and endeavoring to their implementation within a defined timetable until a peaceful transition to a democratic society aspired to by the people."

Abdel-Rahman Samir, one of the protest organizers, said the movement would now open negotiations with the military over democratic reforms but vowed protests would continue to ensure change is carried out.

"We still don’t have any guarantees yet — if we end the whole situation now the it’s like we haven’t done anything," he said. "So we need to keep sitting in Tahrir until we get all our demands."

But, he added, "I feel fantastic. …. I feel like we have worked so hard, we planted a seed for a year and a half and now we are now finally sowing the fruits."

Sally Toma, another of the organizers, said she did not expect the military would try to clear the square. "We still have to sit and talk. We have to hear the army first," she said.

For the moment, concerns over the next step were overwhelmed by the wave of joy and disbelief.

Outside the Oruba presidential palace in northern Cairo, where tens of thousands had marched during the day, one man sprawled on the grass, saying he couldn’t believe it. Protesters began to form a march toward Tahrir in a sea of Egyptian flags.

Thousands from across the capital of 18 million streamed into Tahrir, where protesters hugged, kissed and wept. Whole families took pictures of each other posing with Egyptian flags with their mobile phones as bridges over the Nile jammed with throngs more flowing into the square.

Mahmoud Ghanem, who came from the northern Nile Delta five days ago to join the Tahrir protest camp, proclaimed, "My children can finally live in freedom."

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AP correspondents Hadeel al-Shalchi, Sarah El Deeb, Hamza Hendawi, Marjorie Olster, Tarek el-Tablawy and Maggie Hyde contributed to this report.