Yulia Tymoshenko
Yulia TymoshenkoReuters

Former Ukrainian prime minister Yulia Tymoshenko has announced she will run for president in the 25 May elections.

The bitter political rival of ousted pro-Kremlin Ukrainian president Viktor Yanukovich said she wants "to build the country from scratch to be an example for the world".

"On 29 March there will be a party congress in which I will ask to be nominated for president," she said during a press conference.

The Orange Revolution leader said that Ukraine future "is not possible with oligarchs".

"Ukrainian politicians really don't want to fight local corruption, except me," she added. "Ukrainians feel that nothing has changed after the revolution."

"I'm sure that I will be able to defend Ukraine from Russian agression and to return Crimea!"

The announcement came after a leaked phone call between Tymoshenko and Nestor Shufrych, former deputy secretary of the national security and defence council of Ukraine, made headlines across the world.

The ex-PM allegedly called on her compatriots to "take up arms and kill the f*****g Russians along with their leader [Vladimir Putin]".

The 53-year-old opposition stalwart was freed after the ousting of Yanukovich in February. In emotional scenes from Kiev's Independence Square, Tymoshenko made a rousing speech, overcome by her emotions as she addressed the 50,000-strong crowd.

A constant thorn on the side of Yanukovich, she languished in detention for two-and-half years, accused of an abuse of power in office and linked to a fraudulent gas deal that prosecutors claimed made her millions of dollars.

While she served her sentence, she feared authorities were poisoning her cosmetic products and refused invasive medical treatment. The Ukranian prison service refuted her claims, suggesting no suspicious substances had ever been found.

Western governments said her imprisonment was politically motivated and the European Union repeatedly pressed for her release, only to be rebuffed by Yanukovich. She was released following a resolution by Parliament.

Tymoshenko had served twice as prime minister, after taking power with former president Viktor Yushchenko in Ukraine's Orange Revolution in 2004.

During her time in office, she worked to loosen Ukraine's ties with Russia and take her country closer to the EU but trouble started when the pro-Moscow government of Yanukovich entered office.