UN rights chief Navi Pillay on Thursday demanded a wide-ranging probe into Egyptian security forces\' bloody crackdown on Muslim Brotherhood protesters, joining an international chorus of condemnation. \"The number of people killed or injured, even according to the government\'s figures, point to an excessive, even extreme, use of force against demonstrators,\" Pillay said in a statement. \"There must be an independent, impartial, effective and credible investigation of the conduct of the security forces. Anyone found guilty of wrongdoing should be held to account,\" she added.