An international rights group has decried the prolonged detention and torture of a young detainee in Egypt over allegations that he belongs to the banned Muslim Brotherhood group.

Amnesty International said Friday that Islam Khalil, held for 122 days at an undisclosed location before being taken to prison, was badly tortured with electric shocks into giving confessions that he belongs to the Islamist organization.

Amnesty says Khalil went on hunger strike when prison authorities punished him with solitary confinement and warned that his health is deteriorating.

Egypt's prisons and detention centers are packed with political opponents, who were rounded up in the years after the military's removal of Islamist President Mohammed Morsi in 2013. Opponents say authorities use abductions, torture and other shocking tactics as a tool to stifle dissent.