Eritrea is one of the most repressive, secretive and inaccessible countries in the world. Anyone who challenges President Issaias Afeworki is jailed without trial.
Political opposition is banned, independent media quashed and religious minorities targeted. Reporters Without Borders lists Eritrea below North Korea as the worst country in the world for press freedom
"The government has systematically used arbitrary arrest and detention without charge to crush all opposition, to silence all dissent, and to punish anyone who refuses to comply with the repressive restrictions it places on people's lives," said Claire Beston, Amnesty's Eritrea researcher.
Underground dungeons and shipping containers are used to house the prisoners.