The opposition in the former Soviet republic of Georgia launched what it called a "velvet revolution" Saturday as protesters stormed Parliament, occupied President Eduard Shevardnadze's headquarters and declared their leader the acting head of state.

Armed guards whisked Shevardnadze away from the Parliament building after demonstrators broke into the chamber while he was speaking. Fleeing to a government residence, he called the revolt an "armed coup d'etat," declared a state of emergency and gave the opposition 48 hours to clear out of government buildings.

Armored vehicles surrounded the Interior Ministry late in the evening, but riot police in the streets largely refused to intervene, allowing protesters free rein in the capital of Tbilisi, suggesting that Shevardnadze no longer had full control. Hours after demonstrators took over Parliament, security guards permitted them to enter the government seat of power at the State Chancellery, snatch Shevardnadze's chair from his office, move it outside and burn it.

"We're making a revolution," Zurab Zhvania, a former Parliament speaker and one of three main opposition leaders, said in a telephone interview from Tbilisi. "It was an incredible day. We were not expecting such an outcome, but people were completely galvanized."

Zhvania's successor and ally, Parliament speaker Nino Burdzhanadze, declared herself the country's interim leader until the situation cleared up and called on Shevardnadze to peacefully step aside. As tens of thousands of flag-waving protesters surged through the streets of Tbilisi on Saturday evening, she pledged to guarantee security for Shevardnadze and his family if he resigned.

The dramatic confrontation culminated three weeks of street protests against parliamentary elections that opposition leaders considered rigged. There were no reports of serious violence Saturday, and, contrary to Shevardnadze's claim, no evidence that the opposition was armed. Opposition leader Mikheil Saakashvili and his colleagues entered the Parliament chamber with flowers, according to witnesses.

Shevardnadze took a tough line after being evacuated from Parliament. "If I prove weak now, the people won't forgive me," he told reporters, flanked by the interior minister, who commands domestic troops. "We will restore order and punish the criminals. They will be arrested."

Shevardnadze concluded that he had been too lenient with his opponents. "I'm to blame for much of what's happened, as there's too much I've let them get away with. That is a crime in regard to the people and country. I won't let any of this happen anymore."

He rejected demands that he quit. But he left open the prospect of surrendering his office before his final term expires in 2005. "I can step down only within the framework of the constitution. It will depend on the Parliament and the population, but everything has to happen within the constitutional framework."

Shevardnadze, 75, who earned international renown for his role in ending the Cold War during his days as Mikhail Gorbachev's silver-haired Soviet foreign minister, has become reviled at home after a decade-long tenure spoiled by civil war, poverty and corruption. After years of propping him up with generous financial aid, the United States lately has soured on him for failing to tackle the systemic problems in the nation of 5 million in the Caucasus Mountains.

The U.S. State Department called on all sides Saturday "to refrain from the use of force or violence and to enter a dialogue with a view to restoring calm and reaching a compromise solution acceptable to all and in the interest of Georgia."

The beleaguered Georgian leader appealed to Secretary of State Colin L. Powell to travel to Georgia to help resolve the crisis, U.S. officials confirmed.

The overture came during a telephone call organized by Powell that included U.N. Secretary General Kofi Annan in a bid to help prevent the crisis from deteriorating into violence, according to the State Department.

Powell kept Shevardnadze at arm's length, however. Powell said he would try to visit the former Soviet republic someday, but U.S. officials insisted that he does not currently have travel plans. Powell and Annan instead urged Shevardnadze to peacefully work with the opposition.

U.S. diplomats in Tbilisi also urged the opposition to use restraint, said Richard Boucher, the State Department spokesman. The United States will be "coordinating" with the Russians. he added.

Russian President Vladimir Putin also spoke with Shevardnadze and dispatched Foreign Minister Igor Ivanov to Tbilisi to help mediate. Ivanov arrived in the Georgian capital early Sunday and consulted with government officials, then proceeded to the Parliament building where he met with opposition leaders and addressed their supporters before dawn.

Years of domestic frustration with Shevardnadze finally erupted after parliamentary elections on Nov. 2 were marred by widespread reports of fraud. U.S. and European observers denounced the vote as rigged and opposition supporters have taken to the streets for demonstrations nearly every day since then.

The government election commission took 21/2 weeks to count the votes, finally giving Shevardnadze's party, For a New Georgia, the most votes, or 21 percent. Shevardnadze moved to form a coalition with the second-place finisher, the Revival party, led by a regional chieftain allied with Russia.

Shevardnadze was trying to convene the newly elected Parliament Saturday when demonstrators gathered outside burst into the chamber. As Saakashvili and hundreds of protesters rushed in from one side, security guards grabbed Shevardnadze and moved him out a back door. Appearing disoriented and still clutching his unfinished speech in a shaking left hand, Shevardnadze was put into an armored car and rushed away, flanked by pickup trucks with armed militia.

"It was really spectacular," Georgi Kandelaki, 21, who was one of the first protesters inside the building, said by telephone from Tbilisi. "The army, the police, they were stepping aside at every step. They just said, 'Go ahead, go in.' "

Shevardnadze's office accused the opposition of trying to harm him. "They wanted to attack the president but didn't succeed," his deputy spokesman, Bondu Zenarashvili, said by telephone.

The developments met with approval among some ordinary Georgians, according to interviews from the capital. "We voted for the opposition and most Georgians are for the opposition, but the elections were blocked," said Josef Kumaritov, 24, a recent college graduate. He added, however, "there's still a lot of danger here."

Opposition leaders tried to forestall violence and embraced the language and tactics of peaceful revolutions in Czechoslovakia and Serbia. "The velvet revolution in Georgia has become a fact," Saakashvili told supporters outside Parliament, adopting the name of the 1989 uprising in Prague, the Czech capital. "We don't need any bloody revolution in the country," Burdzhanadze said.

Saakashvili and Burdzhanadze both told CNN that they would guarantee Shevardnadze's safety if he did not respond with force and suggested they would let him remain in office as long as he called presidential and parliamentary elections.

Under the constitution, Burdzhanadze, as Parliament speaker, would succeed Shevardnadze for 45 days if he resigned, pending a new presidential election.

Staff writers Robin Wright in Washington and Colum Lynch in New York contributed to this report.

Supporters and opponents of President Eduard Shevardnadze fight in front of his residence.Opposition supporters break into the Parliament building in Tbilisi, Georgia. Security guards let them take President Eduard Shevardnadze's chair from his office and burn it.