The United Nations' humanitarian news agency IRIN estimates about 1,100 people died in violence since a popular uprising forced Hosni Mubarak from power in early 2011.
Protesters on Monday marked the second anniversary of Mubarak's ouster. Though late January demonstrations were deadly, the Egyptian Independent news agency reports few incidents of violence during the recent commemorations.
Human rights activist Mohamed Bahnasy told IRIN that an investigation was needed given the high number of deaths associated with political unrest.
"We are in dire need of a serious investigation into the violence that accompanied the revolution and the violence that followed it," he said.
The U.S. Embassy in Cairo last week issued an advisory warning that Muslim Brotherhood opponents may direct their anger at U.S. interests.
Egyptian President Mohamed Morsi comes from the Muslim Brotherhood's Freedom and Justice Party. He's faced mounting opposition at home despite winning the support of the international community.
Egyptian news agency al-Ahram reports police were on high alert Monday.
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