The former prime minister, who was convicted of abuse of office in a case widely seen as political revenge by her arch-foe Yanukovych, is a polarizing figure in a country staggering from political tensions that exploded into violence. Admired and even adored by many for her flair and fiery rhetoric, Tymoshenko is regarded by others as driven by intense ego and tainted with corruption.
Just a day after she left the hospital where she was imprisoned, demonstrators outside the Cabinet of Ministers expressed dismay that she could be Ukraine's next president. One of them held a placard depicting Tymoshenko taking power from Yanukovych and reading, "People didn't die for this."
Ukraine is in a delicate state of uncertainty since Yanukovych and protest leaders signed an agreement to end the conflict that left more than 80 people dead last week in Kiev. Soon after signing it, Yanukovych's whereabouts are unclear after he left the capital for his support base in eastern Ukraine. Allies are deserting him.
Russia's next moves in the crisis were not immediately clear, but Washington warned Moscow not to intervene militarily.
The newly emboldened parliament, now dominated by the opposition, struggled to work out who is in charge of the country and its ailing economy. Fears percolated that some regions might try to break away and seek support from neighboring Russia, particularly the Crimean peninsula where Russia's Black Sea naval fleet is based.
Ukraine is deeply divided between eastern regions that are largely pro-Russian and western areas that widely detest Yanukovych and long for closer ties with the European Union.
Yanukovych set off a wave of protests by shelving an agreement with the EU in November, and the movement quickly expanded its grievances to corruption, human rights abuses and calls for Yanukovych's resignation.
The parliament on Sunday assigned presidential powers to its new speaker, Tymoshenko ally Oleksandr Turchinov, who said top priorities include saving the economy and "returning to the path of European integration," according to news agencies. The latter phrase is certain to displease Moscow, which wants Ukraine to be part of a customs union that would rival the EU and bolster Russia's influence. Russia granted Ukraine a $15 billion bailout after Yanukovych backed away from the EU deal.
The Kiev protest camp at the center of the anti-Yanukovych movement filled with more and more dedicated demonstrators Sunday, setting up new tents. Demonstrators posed with an APC and two water cannon that protesters seized during last week's clashes and carried flowers to memorialize the dead, some of whom were killed by snipers.
Tymoshenko, the blond-braided and controversial heroine of the 2004 Orange Revolution, increasingly appears to have the upper hand in the political battle, winning the backing Sunday of a leading Russian lawmaker and congratulations from German Chancellor Angela Merkel and U.S. senators on her release.
Although her spokeswoman, Maria Soroka, said it's too early to discuss whether she will run for president in early elections called for May 25, Tymoshenko is possessed of adamant determination. Even from a wheelchair because of a back problem that was aggravted in 2 1/2 years of imprisonment, she was a powerful speaker Saturday to a crowd of tens of thousands at the protest camp.
"She knows how to do it. She is our hero," said Ludmilla Petrova, one of those at the square the next day.
Other demonstrators objeccted.
"She is just as corrupt as Yanukovych," said 28-year-old Boris Budinok. "We need new faces in Ukrainian politics. The old ones brought us to where we are now."
Tymoshenko's admirers remember her as the most vivid figure of the Orange Rvolution, which forced a rerun of a fraud-riddled presidential election purportedly won by Yanukovych. After the new vote, won by Viktor Yushchenko, Tymoshenko became prime minister.
But she and Yushchenko quarreled intensely and their government was a huge letdown for those who had hoped it would help integrate Ukraine into Europe. Detractors also look askance at her for her years at the helm of Unified Energy Systems, a middleman company that was the main importer of the Russian natural gas on which Ukraine depends. Nicknamed "The Gas Princess," she was accused of giving kickbacks to then-premier Pavlo Lazarenko, who is no imprisoned in the United States for fraud. Later, as deputy prime minister, she pushed through reforms of the energy sector that some said did little more than fill the pockets of her associates.
Susan Rice, President Barack Obama's national security adviser, said he and Russian President Vladimir Putin agreed during a telephone conversation Friday that a political settlement in Kiev should ensure the country's unity and personal freedoms. Rice also said Sunday on NBC's "Meet the Press" that it would be a "grave mistake" for Russia to intervene militarily in Ukraine.
The Kremlin has been largely silent about whether it still supports Yanukovych. Putin, who presided over the close of the Sochi Olympics, has not spoken about recent events in Kiev. He had developed a productive working relationship with Tymoshenko when she was Ukraine's prime minister.
Russia recalled its ambassador from Kiev for consultations because of the developments in Ukraine, the Russian Foreign Ministry said on its website.
The conviction that sent Tymoshenko to prison was for allegedly negotiating an excessively high price for Russian gas.
Russian legislator Leonid Slutsky said Sunday that naming Tymoshenko prime minister "would be useful for stabilizing" tensions in Ukraine, according to Russian news agencies.
Russia's finance minister urged Ukraine to seek a loan from the International Monetary Fund to avoid an imminent default.
Tensions mounted in Crimea, where pro-Russian politicians are organizing rallies and forming protest units and have been demanding autonomy from Kiev. Russia maintains a big naval base in Crimea that has tangled relations between the countries for two decades.
A crowd of pro-Russia demonstrators in the Crimean city of Kerch, following a rally Sunday at which speakers called for Crimea's secession, marched toward city hall chanting "Russia! Russia!" and tore down the Ukrainian flag. Marchers scuffled with the mayor and police officers who tried but failed to stop the crowd from hoisting a Russian flag in its place.
The political crisis in this nation of 46 million has changed with blinding speed in the past week.
In a special session Sunday, the parliament voted overwhelmingly to temporarily hand the president's powers to speaker Turchinov. He stuck with Tymoshenko even as others deserted her in her roller coaster political career.
The legitimacy of the parliament's flurry of decisions in recent days is under question. The votes are based on a decision Friday to return to a 10-year-old constitution that grants parliament greater powers. Yanukovych has not signed that decision into law, and he said Saturday that the parliament is now acting illegally. However, legal experts said that de facto the parliament is now in charge.
Presidential aide Hanna Herman told the AP on Sunday that Yanukovych was in the eastern Ukrainian city of Kharkiv as of Saturday night and plans to stay in power.
Protesters smashed portraits of Yanukovych and took down statues of Soviet founder Vladimir Lenin in several towns and cities. On Sunday, some pro-Russian protesters took up positions to defend Lenin statues in Donetsk and Kharkiv. Statues of Lenin across the former U.S.S.R. are seen as a symbol of Moscow's rule.
Associated Press writers Maria Danilova, Yuras Karmanau and Dusan Stojanovic in Kiev, Lynn Berry in Moscow, and Geir Moulson in Berlin contributed to this report.