Prisoners in Chad are held in such inhumane conditions that "a prison sentence risks becoming a death sentence", Amnesty International says.
In a report, the human rights group says it saw inmates kept in severely overcrowded and unventilated cells during visits to six prisons.
The document details incidents where nine prisoners died of asphyxiation and seven others were shot by guards.
Amnesty says that woman prisoners face constant risk of sexual attacks.
The group also says that its researches saw children as young as seven months old staying with their mothers in cells.
"It is not acceptable for detention conditions to be so poor that a prison sentence risks becoming a death sentence," Amnesty's Chad researcher Christian Mukosa said.
"Most of the prisoners we met were emaciated and weak. Some were chained 24 hours a day... and many suffered skin diseases, sexually transmitted infections, Malaria or TB."
The report urges the authorities of the African country to immediately investigate the alleged abuses.
The government in N'Djamena has so far made no public comments on the issue.