CAIRO - After eight days of protests that killed nearly 60 people, a video of one demonstrator stripped naked, dragged across the ground and beaten with truncheons by helmeted riot police has fired Egyptians to a new level of outrage.

Hamada Saber, a middle-aged man, lay in a police hospital on Saturday, the morning after he was shown on television naked, covered in soot and thrashed by half a dozen policemen who had pulled him to an armored vehicle near the presidential palace.

Egyptian President Mohamed Morsi's office promised an investigation of the incident, which followed the deadliest wave of bloodshed of his seven-month rule. His opponents say it proves that he has chosen to order a brutal crackdown like that carried out by Hosni Mubarak against the uprising that toppled him in 2011.

"Morsi has been stripped bare and has lost his legitimacy. Done," tweeted Ahmed Maher, founder of the April 6 youth movement that helped launch the anti-Mubarak protests.

Another protester was shot dead on Friday and more than 100 were injured, many seriously, after running battles between police and demonstrators who attacked the palace with petrol bombs.

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