The United Nations human rights office says it is concerned over what it calls the "dire state" of Brazilian prisons after video of apparent beheadings in one penitentiary surfaced this week.
The U.N. said Wednesday it is urging Brazilian authorities to conduct a prompt and impartial investigation, and to restore order in the Pedrinhas prison.
Officials in Brazil's northeastern Maranhao state call the decapitations an act of "savagery" and say they are investigating if the video is genuine.
Maranhao officials also blame imprisoned gang leaders for ordering colleagues on the outside to set a city bus on fire to retaliate for a crackdown by prison officials. A 6-year-old girl was killed.
Conditions across Brazil prisons are notoriously brutal because of overcrowding and gang warfare.