The alleged torture during the 18-day uprising included whippings and electric shocks, with one detainee saying he was stripped and dropped upside-down into a barrel of water, Amnesty International said.
The military, which took control of Egypt after President Hosni Mubarak was ousted, "must intervene to end torture and other abuse of detainees, which we now know to have been taking place in military custody," regional Amnesty International Director Malcolm Smart said.
A 29-year-old former detainee from the Gharbiya governorate, between Cairo and Alexandria, said he was stripped Feb. 3 by soldiers in an annex to the Museum of Egyptian Antiquities near Tahrir Square, the focal point of the anti-government demonstrations, Amnesty said.
The soldiers "beat me with a whip and stepped with boots on my back and on my hands. They kicked me. Many other detainees there were also beaten with a whip," Amnesty quoted him as saying.
The unnamed detainee was later beaten in the head with a chair, leaving him unconscious, and moved the next day to another location, where he was beaten, subjected to electric shocks and threatened with rape before being taken to a military prison northeast of Cairo, where he was also regularly beaten by soldiers until his Feb. 10 release, Amnesty said.
An 18-year-old student from Cairo, who said he was also arrested Feb. 3, told Amnesty: "They put a chain or rope to my legs and lifted me up so that my head was hanging down. From time to time they would let me down into a barrel that was filled with water. They told me to confess that I was trained by Israel or by Iran. They also put electric shocks to my body and I fainted."
Cairo's Arabic Network for Human Rights Information, a separate group devoted to promoting freedom of expression across the Middle East and North Africa, said the army still held "hundreds" of people, "but information on their numbers is still not complete."