According to a field hospital set up by protesters, five activists were killed and 300 wounded on Wednesday.
Ukrainian officials confirmed that two protesters had died of gunshot wounds and they were investigating whether police were responsible.
Doctors at the occupied government building where anti-government protesters have been based for the past two months said the two were killed by shots fired by police marksmen between 6am and 8am. The first was killed by rubber bullets, but they said that they were almost certain that the second man was killed by a live round.
Ukrainianskaya Pravda, a newspaper, identified one of the shot men as Sergei Nigoyan, a 20-year-old activist from Dnipropetrovsk. He reportedly died from four wounds to the head and neck.