Egyptian authorities have been accused by a human rights group of being complicit in the torture and sexual abuse of 52 teenagers, jailed for "peacefully" demonstrating against the government.

The Geneva-based pan-Arab rights group, Alkarama, said the 52 youths, aged between 15 and 18, were routinely subjected to torture and sexual abuse by prison guards and military officers in Alexandria's Koum El Dekka prison.

Egyptian authorities must stop this systematic and widespread practice of torture, which ... could make them liable for prosecution for crimes against humanity. Rachid Mesli, Legal Director at Alkarama

Alkarama said the teenagers bore the "signs of torture" and their physical and mental health was degrading "in the appalling hygiene conditions in which they're detained".

The teenagers said they had been subject to electric shocks, including on their genitals, burns with cigarette butts and sometimes rape, while being hung by their hands for hours.

The teenagers also told their lawyers of regular harassment and ill-treatment, including attacks by prison dogs.

Alkarama, which means "dignity" in Arabic, said most showed signs of torture and fractures on their entire bodies.

Rachid Mesli, the legal director at Alkarama, slammed Egypt's legal system and called for urgent safeguards to protect youths in prison.

"The Egyptian authorities must stop this systematic and widespread practice of torture, which, because of its scope, could make them liable for prosecution for crimes against humanity under the Rome Statute."

The group also said it referred the case to the UN special rapporteur on torture, asking Egyptian authorities to investigate the allegations and bring the perpetrators to justice.

Earlier this year, rights activists reported men and women were being tortured and raped while in police custody.