Based on datum released by the World Prison Brief (WPB), a unique database that provides free access to information about prison systems throughout the world. These are the Top 10 Countries in Africa With The Most Prisoners.

1. South Africa, 161,984 prisoners

2. Ethiopia, 111,050 Prisoners

3. Egypt, 106,000 Prisoners

4. Morocco, 79,368 prisoners

5. Nigeria, 67,586 prisoners

6. Algeria, 61,000 prisoners

7. Kenya, 57,000 prisoners

8. Rwanda, 54,279 prisoners

9. Uganda, 48,714 prisoners

10. Tanzania, 34 404 prisoners


Prisoners population of the countries above were derived using data from governmental and other official sources.

http://listwand.com/2017/03/top-10-countries-in-africa-with-the-most-prisoners/

The number of those "detained and awaiting trial" in Nigerian prisons and detention cells outnumber the sum of these top 10 nations imprisoned combined

Oboi

GogetterMD:
The number of those "detained and awaiting trial" in Nigerian prisons and detention cells outnumber the sum of these top 10 nations imprisoned combined

The survey covered everything... including those awaiting trial..