KIEV, Feb. 22 (Xinhua) -- Dramatic changes were witnessed in Ukraine Saturday as the country's parliament ousted President Viktor Yanukovich after more than three months of violent protests, and released Yanukovich's arch-rival Yulia Tymoshenko.

Yanukovich, who insisted he would not step down, has left Kiev for his support base in the country's pro-Russian east, resulting in a political vacuum in the government.

Former Prime Minister Tymoshenko came back again Saturday to the spotlight as she turned herself up in the Independence Square and addressed anti-government protesters in central Kiev, soon after she had been freed from jail.

Yanukovich had warned that he would not accept any parliament decisions as opposition leaders behaved as "gangsters, who terrorize Ukrainian people."

"The events witnessed by our country and the whole world are an example of a coup d'etat," he said, comparing it to the rise of the Nazis to power in Germany in the 1930s.

It was unclear who would fill the vacuum left by Yanukovich as the parliament voted to set early elections for May 25.

The opposition lawmaker Arsen Avakov, one of the leaders of the anti-government protests, was elected Saturday acting interior minister by the parliament until the new unity government is formed.

The parliament also elected Alexandr Turchinov, an ally of Tymoshenko, as new speaker after his predecessor Volodymyr Rybak had resigned due to health reasons.

Opposition website "Ukrainska Pravda" said that Tymoshenko intends to run for president in the May election. However, this information was not confirmed by Tymoshenko yet.

Late Saturday evening, Turchinov said that the protests have reached their goals and urged the activists to end their demonstration.

However, Tymoshenko called on protestors to continue their encampment in the Independence Square.

"You are heroes, you are the best thing in Ukraine!" the opposition icon said in a touching speech to a 50,000-strong crowd in the square, known in Ukrainian as the Maidan.

"In no case do you have the right to leave the Maidan until you have concluded everything that you planned to do," she said, sitting in a wheelchair due to a back problem.

The Independence Square, where a sprawling protest tent camp was set up in December, has been the center stage for the past three months of anti-government demonstration in Ukraine, whose latest escalation has claimed dozens of lives.

The United States and the European Union hailed unanimously the ouster of Yanukovich. The U.S. said Saturday the dramatic ouster of Yanukovich and the release of Tymoshenko could move the country away from violence toward a political settlement.

EU foreign policy chief Catherine Ashton on Saturday welcomed the release of Tymoshenko.

"This comes as an important step forward in view of addressing concerns regarding selective justice in the country," said Ashton in a statement.

Russian Foreign Minister Sergei Lavrov Saturday expressed serious concern over what he called the failure of the Ukrainian opposition to fulfill a peace deal.

"The opposition has not fulfilled any obligations and it has made new demands following the actions taken by armed extremists and rioters, who posed a direct threat to sovereignty and the constitutional system of Ukraine," Lavrov said during a telephone conversation with foreign ministers of Germany, Poland and France.

Lavrov urged three Western ministers, who mediated and witnessed the signing of the crisis settlement agreement on Friday, to use their influence upon the opposition to stop the violence immediately, the foreign ministry said in a statement.