The escalating violence has alarmed the West, where leaders have long looked to Egypt as a stabilizing force in the region.
French President Francois Hollande and German Chancellor Angela Merkel called for a meeting next week of European Union foreign ministers to coordinate a response to the violence in Egypt.
The EU's foreign policy chief, Catherine Ashton, called the rising casualty toll "shocking."
"Responsibility for this tragedy weighs heavily on the interim government, as well as on the wider political leadership in the country," she said.
Egyptian authorities rejected criticism from U.S. President Barack Obama and other world leaders on Wednesday's ferocious clashes, which left at least 580 people dead after security forces broke up huge sit-ins in Cairo, according to the Health Ministry.
Obama, who has resisted calls to cut off military aid to Egypt and label Morsy's ouster a coup, on Thursday stressed the United States would not support one political faction over another. Even predominantly Muslim nations voiced displeasure, with Turkey recalling its ambassador in Egypt in light of the crisis, a Turkish foreign ministry representative said.