Footage said to have been shot last month by members of the Myanmar police in the town of Meiktila, and obtained by the BBC, shows a badly burnt man lying helplessly on the ground, unassisted by passers-by and policemen.
"Pour water on him," one man says. Another voice orders: "No water for him. Let him die."
In another scene, also shot last month, Buddhist men drag from the undergrowth a young man or boy who is struck repeatedly, and apparently fatally, with sticks and a sword.
The film emerged as European governments dropped sanctions against Myanmar that were temporarily suspended a year ago in recognition of reforms by the government of President Thein Sein.
The 27-nation bloc lifted all sanctions except those against the sale of arms and equipment that can be used for internal repression. Almost immediately Myanmar pardoned at least 59 political prisoners, said Bo Kyi of the Assistance Association for Political Prisoners.
Senior Myanmar diplomat Aung Lynn told reporters at an Association of Southeast Asian Nations conference in Brunei's capital, Bandar Seri Begawan, that the international community can expect more reforms.
"This is a very good beginning," he said.
It came on the same day as a damning report by Human Rights Watch, which accuses the Burmese government, as well as local authorities and Buddhist monks, of crimes against humanity and the ethnic cleansing of Muslims in Rakhine state.
Since coming to power in March 2011 at the head of a notionally civilian government, Mr Thein Sein has presided over unprecedented relaxation of government oppression. Censorship has been eased, protest has been permitted, and hundreds, but not all, of political prisoners have been released.
The former political prisoner and democracy leader Aung San Suu Kyi and her party, the National League for Democracy, have a small number of seats in Myanmar's parliament. Mr Thein Sein has been rewarded by visits from heads of government.
But since last year, his credibility has been undermined by outbreaks of violence in which his security forces are accused of conniving. Myanmar army attacks on rebels in Kachin state have killed civilians and created tens of thousands of refugees. There were reports yesterday of army attacks on villages in northern Shan state, injuring and displacing civilians.
In Meiktila, and in Rakhine state, 125,000 members of the Rohingya Muslim minority have been driven from their homes.
