At least 525 people were killed in yesterday's assaults on two Cairo protest camps of supporters of ousted Islamist president Mohammed Morsi in the worst violence the country has seen in decades.
The United States led global condemnations overnight against the "deplorable" violence, while Paris, London and Berlin have summoned Egypt's ambassadors to voice their strong concern.
Turkey's Prime Minister Recep Tayyip Erdogan called for an urgent UN Security Council meeting over Egypt's "massacre" of Morsi supporters.
Only two Gulf states that have cracked down on Islamist groups within their own borders initially voiced support for the Cairo military leaders.
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French President Francois Hollande said "everything must be done to avoid a civil war" in Egypt, while his government conveyed France's "great concern over the tragic events" to Egypt's envoy.
"France is committed to finding a political solution and calls for elections to be held as soon as possible, in line with the commitments made by Egypt's transitional authorities," said a statement.
"On the orders of Foreign Minister Westerwelle, the ambassador was told the position of the German government in no uncertain terms," said a foreign ministry spokeswoman.
Turkey's Erdogan, a Morsi supporter, told reporters in Ankara that "the Security Council of the United Nations should convene quickly to discuss the situation in Egypt".
"This is a very serious massacre... Against the Egyptian people who were only protesting peacefully," he added, criticising "the silence" of the global community in the face of the bloodshed.