Inmates at Venezuela's western Barinas prison staged a protest on the roof on Sunday, piling flaming mattresses and calling for the removal of the prison director, whom they accused of overseeing guards who shot unarmed prisoners.
"We want justice. They are shooting us, the guards and the wardens," a prisoner said in a video shared by the Venezuelan Prison Observatory, showing a man with a bullet wound in his chest.
Inmates said they were peacefully protesting when prison staff opened fire, leaving some wounded.
Venezuelan authorities did not immediately respond to requests for comment.
Inmates called for the removal of recently appointed director Elvis Macuare Guerrero, saying their clothes were taken away, visits were banned, and they were pressured to sell drugs.
Family members clashed outside with National Guard officers armed with riot shields as they attempted to stop them entering.
The NGO said it is documenting the events and reporting them to human rights watchdogs.
Venezuelan prisons face international scrutiny amid political tensions.
