The White House has strongly condemned Egypt's interim government for using violence against supporters of ousted Islamist President Mohamed Morsi.
In a briefing to reporters Wednesday in Massachusetts, where President Barack Obama is vacationing, White House spokesman Josh Earnest said the United States has repeatedly called for Egyptian security forces to show restraint.
He also repeated calls for the mostly Islamist protesters to "demonstrate peacefully."
Egypt's military-backed interim government launched a deadly crackdown on pro-Morsi protest camps in Cairo earlier in the day, triggering condemnation from leaders of Muslim nations that backed the deposed leader.
European powers also urged the Egyptian government and its Islamist opponents to avoid an escalation of violence and return to a political dialogue.
Earnest said the White House opposes Cairo's imposition of one-month state of emergency in response to escalating unrest in the country.
He said the violence will only make it more difficult for Egypt to move on path to lasting stability and democracy and runs "directly counter" to the interim government's pledges to pursue national reconciliation.
Turkish Prime Minister Recep Tayyip Erdogan described Wednesday's crackdown by Egyptian security forces 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.
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.
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.
Qatar, a supporter of Mr. Morsi's Muslim Brotherhood movement, denounced Egypt for using force against what it said were "peaceful protesters."
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.
Rights group Amnesty International called for the Egyptian military to stop attacking the protesters. Amnesty's Egypt specialist Geoffrey Mock told VOA that Wednesday's violence shows that "old patterns of abuse" that date back to the Mubarak regime are being repeated.