Yulia Tymoshenko arrived in Kyiv on Saturday evening after flying from the Kharkiv region, where she was being held in custody in hospital.

Seated in a wheelchair, she tearfully addressed protesters in Independence Square, also known as the Maidan. "I dreamt of this day, I dreamt of seeing your eyes. You are heroes, you are the best sons of Ukraine."

"When I came to Kyiv I just couldn’t recognize this city - the barricades, the burnt cars - but this country is now free; you gave this country its freedom," she said, adding that those responsible for scores of deaths in recent days would be brought to justice.

"No-one will escape the responsibility," said Tymoshenko. "We have to bring to justice anyone who shot these heroes of Maidan." In a trembling voice, she urged protesters to stay in Independence Square and keep up the pressure for change.

'No drop of blood forgotten'

Upon her release, the 53-year-old, who has been suffering from a back complaint, said she would stand for the office of president after parliament voted for fresh elections. Referring to the scores of people who died in protests during the past week, she said she would "make it so that no drop of blood that was spilled will be forgotten."

Tymoshenko's daughter Yevhenia had earlier welcomed a vote in parliament on Saturday to free the former prime minister.

Tymoshenko has served more than two years in prison after being convicted on a charge of abuse of office, for which she was sentenced to seven years. The trial was internationally condemned as being politically motivated. She was the charismatic leader of the 2004 Orange Revolution, and challenged Yanukovych in a bitterly contested presidential election in 2010.

Two of Tymoshenko's close political allies were on Saturday named as interim prime minister and speaker of parliament.

Yanukovych 'barred' from exit

Border police were reported to have blocked Yanukovych from flying to Russia. "He tried to take a plane to Russia but he was blocked in doing so by border police. He is currently hiding somewhere in the Donetsk region," the Ukrainian news agency Interfax reported the new speaker, Oleksandr Turchyno, as saying.

In the eastern city of Kharkiv earlier, Yanukovych said he would not leave the country and that he had no intention of resigning after parliament voted to oust him. As protesters seized his offices, he compared events in the capital - which he described as a coup - to the coming to power of the Nazis in 1930s Germany.

"Everything happening today can primarily be described as vandalism, banditry and a coup d'etat. That is my assessment," Yanukovych said.

"This is not an opposition," he said. "These are bandits." Yanukovych added that his car had been targeted by a gunman, although he showed no signs of injury. "I feel sorrow for my country," he told UBR television.

Ukraine's army on Saturday had ruled out playing any part in the crisis currently gripping the country. "The army will in no way become involved in the political conflict," it said in a statement.

For the past three months, pro-European demonstrators have turned Kyiv’s Independence Square into a rallying point, demanding fresh elections. Opposition to Yanukovych turned to unrest - with an estimated 88 deaths in recent days - after the president backed out of an association treaty with the European Union in November, instead opting to strengthen ties with Russia.

International leaders urge cooperation

Foreign leaders hailed Tymoshenko's release on Saturday, while also calling on the interim leadership to implement reforms swiftly and justly.

"We need a lasting solution to the political crisis," EU foreign policy chief Catherine Ashton said. "This must include constitutional reform, the formation of a new inclusive government and the creation of the conditions for democratic elections."

Germany's foreign minister, Frank-Walter Steinmeier, who played a prominent role in peace negotiations, also urged opposition politicians to "keep a sense of proportion."

"I urge those with responsibility to halt the political escalation…Maintaining channels of communication and being willing to compromise given the situation and regional differences are more vital than ever," Steinmeier said.

The United States has offered to assist Ukraine to rebuild its economy following the months of crippling protests.

At a meeting with Russian Finance Minister Anton Siluanov on the sidelines of the G20 meeting in Sydney, US Treasury Secretary Jacob Lew said the US "stands ready to assist Ukraine as it implements reforms to restore economic stability and seeks to return to a path of democracy and growth." His remarks were reported by a US Treasury official.

Meanwhile, Moscow, which had backed President Yanukovych's government, criticized the developments.

"Illegal extremist groups are refusing to disarm and in fact are taking Kyiv under their control with the connivance of opposition leaders," Foreign Minister Sergei Lavrov said during a phone conversation with US Secretary of State John Kerry.

The Russian foreign minister also called his German counterpart to exercise his influence over the opposition in order to "change the situation [in Kyiv] immediately."

rc/jm (AP, AFP,dpa, Reuters)