At least 17 prisoners have died in over the past week in the Democratic Republic of Congo’s main prison, the Bill Clinton Foundation for Peace says.
The organisation, which has no affiliation to the foundation set up by former US President Bill Clinton, said the cause was a lack of food and medicine.
Makala Prison in the capital, Kinshasa, which houses more than 8,000 inmates, has received no food supplies for the last two months, Congolese officials say.
So inmates have to rely on their families to bring in meals.
The prison is severely overcrowded - it has five times the number of prisoners it was built for.
Conditions are so poor that non-governmental groups estimate at least 100 prisoners are gravely ill and close to death.
Only 6% of the prisoners are actually serving sentences - the rest are stuck in DR Congo’s legal system where cases can take years.
DR Congo’s deputy minister of justice told local media that Makala had now received some funding to help improve conditions.
He promised more money would follow, but human rights organisations remain sceptical.