Two protesters died after being shot and a third fell from a high level during continuing trouble in Kiev.
The bodies were found after police began dismantling barricades near a government district in Kiev while protesters battled to push them back to their original positions.
Ukraine's political crisis reached a new phase last week after president Viktor Yanukovych pushed through harsh anti-protest legislation.
That prompted street battles at a cordon of riot police and buses near the Ukrainian parliament. Protesters threw rocks and fire bombs and police responded with tear gas and rubber bullets.
The clashes injured hundreds of protesters and police, but the deaths are likely to stoke anger and cause more people to join the protests and clashes.
Mr Yanukovych refused to meet Vitali Klitschko on Tuesday after the boxer turned opposition leader went to his office hoping for negotiations.
The snub dimmed hopes for a resolution to the political crisis as Mr Klitschko said: "The centre of the city of Kiev has been burning for two days. The president sits two blocks away and does not hear it."
Prime minister Mykola Azarov said opposition leaders should be held responsible for the deaths and added that police at the site of the clashes did not have live ammunition.
But Oleh Musiy, co-ordinator of the protesters' medical corps, said the wounds resembled those caused by live ammunition.
The US Embassy said it was revoking the visas of some Ukrainian officials linked to the violence and was considering further action.
The crisis began in late November after Mr Yanukovych stepped back from signing a long-anticipated co-operation deal with the EU. That set off round-the-clock protests in Kiev's central square, where protesters have set up an extensive tent camp.