KIEV - Viktor Yushchenko was sworn in as president of Ukraine on Sunday, calling his inauguration a victory of freedom over tyranny and declaring the country was "now in the center of Europe."

Two months after massive protests over his loss in a fraud-plagued election plunged the nation into political crisis, Yushchenko took the oath of office in a solemn ceremony at the Verkhovna Rada parliament, placing his hand on a copy of the Constitution and on an antique Bible.

With his hand on his heart, he joined in singing the national anthem. Some deputies cheered after the oath and chanted "Yushchenko!" but others stood stonily not applauding, an indication of the deep political tensions Yushchenko faces as leader.

Heading then to Independence Square, where his supporters had protested for weeks, Yushchenko was greeted with louder chants of approval from a huge orange-clad throng that had waited for him for hours in freezing temperatures.

"The heart of Ukraine was on Independence Square," Yushchenko told the shoulder-to-shoulder crowd, which police estimates put at more than 100,000. "Good people from all over the world, from far away countries, were looking at Independence Square, at us."

"This is a victory of freedom over tyranny. The victory of law over lawlessness," he said, standing in the Independence Monument's rotunda, backed by a banner of orange, the campaign color that led to the demonstrations being dubbed the "Orange Revolution."

"Ukraine has opened a new page in the history of Europe," the Western-oriented reformer said, his voice firm. "We are now in the center of Europe."

"Our place is in the European Union. My goal is Ukraine in a united Europe. Our road into the future is the road on which a united Europe is headed," said Yushchenko, his face still swollen and scarred with lesions from his dioxin poisoning in September, which he has said was an attempt to kill him.

He promised to turn the country around after years of corruption, poverty and oppression, and pledged to safeguard freedom of speech.

"We will create new jobs. Whoever wants to work will have the opportunity to work and get an appropriate salary," he declared. "We will fight corruption in Ukraine. Taxes will be enforced, business will be transparent, ... we will become an honest nation."

In a promise clearly aimed at appeasing the country's large native-Russian-speaking population, who widely opposed him, Yushchenko said, "Everyone can teach his children the language of his forefathers."

In the hours before the inauguration, 35-year-old spectator Bohdan Mysorsky had waited in the square and exulted in Yushchenko's achievement. "This is the end of the big game. After this, with Yushchenko Ukraine has the opportunity to become a real state, a real nation -- not Russia's backyard," he said.

Polish President Aleksander Kwasniewski, left, Powell and Havel attending inauguration festivities in central Kiev on Sunday.

Yushchenko was declared the loser of a Nov. 21 election that international observers said was badly tarnished by vote fraud. Hundreds of thousands of demonstrators poured into Kiev's streets to protest the fraud and demonstrations went on for weeks.

The Supreme Court annulled the election and Yushchenko won a Dec. 26 court-ordered rerun, beating Prime Minister Viktor Yanukovych, then the Kremlin-supported prime minister, by 8 percentage points. Yanukovych raised a series of legal challenges to the rerun of the vote, the last of which was rejected by the Supreme Court on Thursday.

Yanukovych has vowed to take his complaints to the European Court of Human Rights. The court has no enforcement mechanism, but such a move could be a shadow on Yushchenko's intentions to push for Ukraine's closer integration with the European Union and NATO. NATO Secretary-General Jaap de Hoop Scheffer was one of many dignitaries, including representatives of more than 40 countries, who came to the inauguration.

Vaclav Havel, the main figure of Czechoslovakia's 1989 "Velvet Revolution" that peacefully overthrew communism, also was in Kiev to watch Yushchenko take office.

Also there was Georgian Parliament Speaker Nino Burdzhanadze, a leader of the 2003 protests that forced a government change in her country and that became a model for Ukraine's demonstrators.

U.S. Secretary of State Colin Powell met with Yushchenko on Sunday before the inauguration.

"The United States wants to do everything we can to help you meet the expectations of the Ukrainian people after this turmoil," Powell said at the start of the meeting.

In contrast, Russia sent relatively low-level representation -- Federation Council Speaker Sergei Mironov.

U.S. President George W. Bush called Yushchenko on Saturday to congratulate him on his election and on "democracy's victory" in Ukraine, White House spokesman Brian Besanceney said in Washington.

Among the challenges Yushchenko faces is likely to be substantial opposition in the country's east, the stronghold of support for Yanukovych, who had been expected to move Ukraine closer into Russia's sphere of influence.