Rights groups say that the use of torture by the Egyptian authorities is so widespread and systematic as to amount to a crime against humanity.

In a report submitted to the UN Committee against Torture, six groups spoke of beatings, electric shocks, sexual violence and denial of access to medical care by members of the security services.

They said torture has been used as a political tool to curtail dissent.

The new chairman of the United States Senate Foreign Relations Committee, Ben Cardin, has threatened to block US military aid to Egypt if Cairo did not take concrete steps to improve its record on human rights.

During his decade-long rule, Egypt's President Abdel Fattah al-Sisi has overseen a crackdown on dissent.