The Egyptian government's deadly crackdown on supporters of former Islamist President Mohamed Morsi has drawn condemnation from leaders of Muslim nations who backed the ousted leader.
European powers urged the military-backed interim government and its Islamist opponents to avoid an escalation of violence and return to a political dialogue.
Turkish Prime Minister Recep Tayyip Erdogan described Wednesday's crackdown by Egyptian security forces on pro-Morsi protest camps in Cairo as a "massacre." He urged the U.N. Security Council and the Arab League to act immediately to stop it.
Turkish President Abdullah Gul accused the Egyptian government of staging an armed intervention against civilians and called that "unacceptable." Egyptian authorities said some of the protesters were armed and fired at security forces.
Ankara was one of the strongest international critics of the Egyptian military's decision to oust Morsi on July 3, one year after he took office as Egypt's first democratically elected leader.
The military said it acted in response to what it called the will of the people after mass protests by secular Egyptians who accused Morsi of being anti-democratic.
A spokesman for U.N. Secretary-General Ban Ki-moon said the U.N. chief condemns the violence in Egypt in the strongest terms, and regrets that Egyptian authorities chose to use force against the mostly Islamist demonstrations.
However, the spokesman also said the U.N. chief also is "well aware that the vast majority of the Egyptian people [are] weary of disruptions to normal life caused by demonstrations and counter-demonstrations, and want their country to go forward peacefully in an Egyptian-led process."
Iran joined Turkey in condemning the Egyptian crackdown as a "massacre." The Fars news agency quoted the Iranian foreign ministry as warning Egypt that if it does not change course, Israel and "arrogant" world powers will derail the Egyptian people's revolution.
Iran's Islamist leadership began reaching out to regional rival Egypt after a 2011 popular uprising deposed Egypt's longtime secular ruler, President Hosni Mubarak, and paved the way for Morsi's election a year later.
Qatar, a supporter of Morsi's Muslim Brotherhood movement, denounced Egypt for using force against what it said were "peaceful protesters." In a statement, the Qatari foreign ministry called on Egyptian authorities to "preserve the lives" of the demonstrators.
In Brussels, EU spokesman Peter Stano said the reports from Cairo were "extremely worrying." He said violence will not lead to solutions, and urged all parties to "exercise maximum restraint."
British Foreign Secretary William Hague took a tougher line against the Egyptian government, saying he condemns its use of force in clearing the protests. He said leaders on all sides "must work to reduce the risk of further violence."
Some information for this report was provided by AP, AFP and Reuters.