Former oligarch Mikhail Khodorkovsky, addressing thousands of people at the cradle of the uprising against Ukraine's Moscow-backed leader, accused Russia on Sunday of being complicit in police violence against protesters.
To chants of "Russia, rise up", Khodorkovsky, who was jailed for a decade under President Vladimir Putin, told the crowd the Kremlin was lying to its own people by portraying the protesters as "neo-fascists" bent on violence.
Wearing a simple dark anorak and jeans, he addressed the crowd from a stage in Kiev's Independence Square, occupied by protesters since November despite police trying to oust them with force which resulted in about 100 deaths.
"I have been shown what the authorities did here. They did this in agreement with the Russian authorities - more than 100 dead, more than 5,000 wounded," Khodorkovsky told the crowd, who waved back with Ukrainian flags.
"I've seen the plywood planks they used to stand up to the bullets. It made me want to cry, it's so awful," he said, his voice shaking with emotion.
The 50-year-old former executive, who fell out with Putin more than a decade ago, said it was clear that the Kremlin leader's portrayal of the protesters as dangerous extremists, drummed home by Russia's state-controlled media, was false.
"Russian propaganda lies, as always. There are no fascists or Nazis here, no more than on the streets on Moscow or St Petersburg," he said. "These are wonderful people who stood up for their freedom."
His remarks are likely to rile Putin because they undermine the Kremlin leader's position in a standoff with the United States and the European Union over Crimea, the Ukrainian Black Sea peninsula seized by Russian forces.
Putin's justification for saying Russia has the right to invade Ukraine if necessary is based on the premise that Russians and Russian-speakers in the former Soviet republic are threatened by "neo-fascists".
Putin denies his country is a participant in the conflict in Ukraine and denies Russia's armed forces are involved in Crimea, an assertion ridiculed in the West.
OFFER TO MEDIATE
Khodorkovsky arrived in Ukraine after offering to mediate in the Crimea crisis, saying he was worried the country was on the brink of civil war. He will deliver a lecture on Monday in Kiev, the capital, but there is no indication that anyone has taken up his offer to mediate.
Although he was arrested at a time when corruption was particularly rife in Russia, Khodorkovsky was widely regarded abroad as a political prisoner after being arrested at gunpoint in 2003 and convicted of theft and tax evasion in 2005.
His oil company, Yukos, was broken up and sold off, mainly into state hands. Eventually pardoned and freed by Putin in December, he left the country immediately, saying he would not get involved in politics.
His speech on Sunday, however, was highly political and fiercely critical of Putin, with whom he fell out after defying an order to wealthy businessmen to stay out of politics.
"I want you to know there is another Russia," Khodorkovsky told the crowd, which responded at the end of his speech by chanting "Well done."
"There are people who despite the arrests, despite the long years they have spent in prison, go to anti-war demonstrations in Moscow, people for whom friendship between the Russian and Ukrainian people is stronger than their own freedom," he said.