Summary Tymoshenko had lost a close presidential poll to Yanukovych in 2010.
KIEV (AFP) - Ukraine s divisive opposition icon Yulia Tymoshenko completed an improbable return to politics on Thursday by announcing plans to contest snap polls to replace the ousted pro-Russian president whose regime sent her to jail.
"I intend to run for president of Ukraine," the 53-year-old told reporters after gingerly walking into a press room with the help of a walking stick she uses due to chronic back pain.
The brief but dramatic announcement encapsulates the spectacular changes that have swept the economically struggling and culturally splintered ex-Soviet state of 46 million in the past few weeks.
Tymoshenko -- one of the most charismatic and outspoken leaders of Ukraine s 2004 pro-democracy Orange Revolution -- lost a close presidential poll to Yanukovych in 2010 after heading two pro-Western cabinets that became embroiled in internal disputes and eventually lost popular support.
Her political downfall after the 2010 vote was rapid and seemingly fatal.
Yanukovych s government quickly launched a series of criminal probes against his political rival that led to a controversial trial over Tymoshenko s role in agreeing a 2009 gas contract with Russia that many Ukrainians thought came at too high a price.
Tymoshenko was convicted in October 2011 for abuse of power and sentenced to a seven-year jail term that Western nations denounced as politically motivated.
But she emerged triumphantly from the state hospital in which she had spent most of her sentence under guard on February 22 -- the day parliament ousted Yanukovych for his role in the deaths of nearly 100 protesters in Kiev earlier that month.
Tymoshenko then immediately went to the protest square in the heart of Kiev -- a return to the crucible of the 2004 pro-democracy movement that propelled her political career.
The crowd s reception of the one-time opposition icon was guarded. Many remained wary of the ugly corruption allegations that have stained Tymoshenko s reputation.
Some analysts believe the pro-Western movement that Tymoshenko once headed is now looking to a new generation of leaders who played a more prominent role in the latest protests and who now hold key positions in the new interim government.
- I stand out -
Tymoshenko on Thursday attempted to paint herself as a compromise figure who could look after the interests of her old supporters while reassuring Russian speakers, particularly in Ukraine s southeast, who have traditionally relied on the Kremlin for support.
"I will be able to find a common language with everyone who lives in the east," Tymoshenko said before adding that she still viewed Russian President Vladimir Putin as "Ukraine s enemy number one".
Critics have long accused Tymoshenko of being a political chameleon, lacking ideals and frequently changing her positions in her thirst for power.
Putin has famously said that he viewed Tymoshenko as a trusted partner with whom he could do business despite her seeming allegiance to closer ties with the West.
Tymoshenko on Thursday vowed to commit herself to breaking the close links between big business and government that have allowed a select group of tycoons and political insiders to enrich themselves through shadowy deals.
"I stand out from all the other presidential candidates because I will actually be able to do this: I will be able to break up these huge clan-like corporations," she said.
Tymoshenko has considerable ground to make up if she hopes to win the May 25 election. A poll published on Wednesday by four respected Ukrainian research firms put her in third place with 8.2 percent of the prospective vote.
Chocolate baron Petro Poroshenko ranked first with the backing of 24.8 percent of respondents.
Former boxing champion turned opposition leader Vitali Klitschko was second with 8.9 percent.
But some analysts said Tymoshenko still had the political wherewithal to mount a powerful challenge that should at least secure her a place in a second-round runoff.
"Tymoshenko knows how to wage a political campaign," said Kiev s Global Strategies Institute director Vadym Karasyov.
"It is much too premature to speak of a clear winner in this election."
