Campaign group Human Rights Watch says the authorities in the Democratic Republic of Congo repeatedly ignored security warnings which preceded a prison riot last year in which inmates raped dozens of female detainees, including a teenage girl.
About 2,000 detainees of Kasapa prison in the city of Lubumbashi rioted in September 2020, setting fire to buildings and attacking female inmates for three days.
Several of the victims became pregnant and some contracted HIV.
Security forces reportedly shot dead at least 20 people during the riot.
It says survivors must be given medical care and mental health support.