GENEVA -- The U.N.'s top human rights official on Tuesday praised the protest movement in Egypt and called on authorities to change a system that encourages abuses of the country's people, in an unusually frank call from a U.N. official.

"The whole world is watching how the president and the reconfigured government will react to the continuing protests demanding a radical change," the U.N. High Commissioner for Human Rights, Navi Pillay, said in a statement.

"The population appears to be clearly rejecting a system that has deprived people of fundamental rights, and has committed a range of serious abuses, including widespread acts of torture," Pillay said.

Thousands of people were gathered on the streets of Cairo to demand the ouster of President Hosni Mubarak, who is blamed for ignoring the needs of the poor and allowing corruption and official abuse to run rampant during his nearly 30 years in power.

Pillay expressed alarm at reports that 300 people have been killed and more than 3,000 injured in the protests that have gripped Egypt since last week.

"I urge the Egyptian authorities to ensure police and other security forces scrupulously avoid excessive use of force," she said. She urged investigations into the role of security forces during the violence and their sudden disappearance from the streets of Cairo, leaving what she described as a "security vacuum."

"People must not be arbitrarily detained, simply for protesting or for expressing their political opinions, however unwelcome those opinions may be to those in power," she added.

Pillay said the Egyptian government should stop interfering with communications, Internet and transport systems, as well as news organizations covering the protests.