A video showing a group of Egyptian riot police beating a naked man with batons has fired outrage in the country off the scale.
The last eight days have been the bloodiest since President Mohammed Mursi came to power with close to 60 people being killed following unrest in a number of cities.
Political instability and street protests threaten to make the most populous Arab state ungovernable.
The victim of the brutality, Hamada Saber, is said to be recovering from his injuries in a police hospital.
The president’s office released a statement announcing an investigation into the beating.
There is anger on the streets of Cairo:
“This is against humanity, nobody accepts it. The officers who carried out the beating may one see a member of his family beaten in the same way. We condemn what happened even if the victim was thief or a thug,” said one man.
The main opposition coalition has called for an end to the regime and want Mursi to stand trial.
Opponents of the president claim he ordered the crackdown like that carried out by Hosni Mubarak during the uprising that forced him from office.
The latest wave of violence was triggered by the second anniversary of the fall of Mubarak and the death sentences handed down in Port Said over a riot at a football stadium that left 70 people dead.