Geneva: UN rights chief Navi Pillay on Thursday demanded a wide-ranging probe into the bloody crackdown by Egyptian security forces on Muslim Brotherhood protesters.,
"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," Pillay said in a statement.
More than 500 people, according to government figures, were killed in Wednesday's assaults on two Cairo protest camps of supporters of ousted Islamist president Mohamed Morsi in the country's worst violence in decades.
The Muslim Brotherhood has put the death toll at more than 2,000.
"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.
Adding her voice to the global outcry over the bloodshed, Pillay urged "all sides in Egypt to step back from the brink of disaster."
"I deplore the loss of life and call on all in Egypt to seek a way out of the violence," she said.
Pillay urged the Egyptian authorities and security forces "to act with the utmost restraint," saying they were "bound by the rule of law and must act with full respect for human rights."
The UN rights chief also said she was deeply worried by reports of government opponents attacking public buildings and religious sites, insisting that those responsible should be brought to justice.
"Wednesday's tragic events highlight the degree to which Egypt is becoming dangerously polarised," she said, appealing to all sides to "engage in urgent dialogue to avoid further violence and hate speech, with the aim of restoring constitutional order through free and democratic elections".
Pillay also said the month-long state of emergency imposed by the authorities must conform with Egypt's obligations under international law.
"Everyone deprived of their liberty must be treated humanely and afforded all the judicial guarantees under international law," she said.