Pillay said Tuesday she was alarmed by the escalation of violence in Egypt. Post-revolutionary frustrations boiled over last week as demonstrations marking the 2011 uprising turned violent. The violence was compounded by a court ruling regarding a riot in Port Said.
Pillay said she was frustrated with what she said was the use of excessive force to curb the violence.
"As the tragic events over the past few days have shown, Egypt remains extremely fragile and unstable, and I urge the government to make a much stronger effort to accommodate opposing points of view and take concrete actions to address public concerns," she said in a statement Tuesday.
Opposition groups in Egypt said they weren't interested in negotiating with Egyptian President Mohamed Morsi. His administration has faced criticism that it is influenced too much by his affiliation with the Muslim Brotherhood.
U.S. State Department spokeswoman Victoria Nuland said Washington was frustrated by the escalation of violence but "gratified" that Morsi issued a call for national dialogue.
Morsi was hailed by Western governments for his role in brokering a recent truce between Hamas militants and Israel.