An Egyptian man dragged naked through the streets of Cairo by police has admitted security forces were to blame, after earlier blaming protesters.Hamada Saber's beating by uniformed officers was filmed and aired on state TV on Friday as angry crowds targeted the presidential palace.From his police hospital bed the 50-year-old painter initially said protestors had stripped and beaten him, with police coming to his rescue.But he later said police were to blame.He said that he had been coerced into giving a false account. His son told the BBC that had he accused the police, they would have accused him of carrying petrol bombs at the demonstration.Mr Saber said police had subsequently apologised to him for any wrongdoing.Islamist President Mohammed Morsi has condemned the isolated incident and, in an unusual move, called for an enquiry.But government opponents say the "crime against humanity" has "dire consequences for justice"."That he be forced to amend his testimony before the Public Prosecution is tyranny," tweeted Nasser Amin, a lawyer and campaigner for judicial independence.'Collapse of the state'Friday's clashes saw police using tear gas and water cannon against rock-throwing protesters after a week of violence in which dozens died.One person was reportedly killed and more than 50 injured.The protesters accuse Mr Morsi of betraying the aims of the 2011 uprising - a claim he denies.In a statement on his Facebook page, the president warned that security forces would "act with utmost decisiveness" to protect state institutions and those groups behind the violence would be held "politically accountable".The current unrest began on 24 January in Cairo on the eve of the second anniversary of the revolution and has spread to several cities.On Tuesday, Egyptian army chief Gen Abdul Fattah al-Sisi warned that the political crisis could lead to the collapse of the state.