Egyptian prosecutors Wednesday ordered arrests of 10 Islamists, including Muslim Brotherhood Supreme Guide Mohamed Badei and other members of the organization, on charges of inciting Monday's violence at the Republican Guard headquarters in Cairo that left 51 dead and at least 435 injured when the army opened fire on supporters of deposed President Mohamed Morsi, Ahram Online reported.
One Egyptian army officer was killed and 42 soldiers were injured, officials said. At least 200 of the 652 people detained as suspects are being held in jail for 15 days as prosecutors investigate the deadly incident.
"We are working with our allies in the region to reinforce the message that we have been sending to those in Egypt about the need for Egypt to get off a path of polarization and move forward on a path of reconciliation," he said.
"And we are doing all this amidst an obviously very fluid situation and one that puts Egypt's future at stake."
Carney reiterated U.S. opposition to "arbitrary arrests," and said "the way to move Egypt beyond crisis and toward a better future is for the authorities to embrace a process that is inclusive, that leads to a transition back to a civilian, democratically elected government, and that responds to the hopes and aspirations of the Egyptian people, of all the Egyptian people."
Badei and Muslim Brotherhood Deputy Guide Mahmoud Ezzat, member Mohamed el-Beltagy, Freedom and Justice Party Vice Chairman Esam el-Erian, al-Gamaa al-Islamiya Assem Abd el-Maged and Brotherhood supporter Safwat Hegazy were charged with "planning, inciting and aiding criminal acts."
Wasat Party Vice Chairman Essam Sultan, al-Gamaa al-Islamiya Building and Development Party Vice Chairman Safwat Abd el-Ghany, Islamist activist Abd el-Rahman Ezz and Brotherhood council member Mahmoud Hussein were also charged.
Ahram Online said the official army statement said an "armed terrorist group" of pro-Morsi protesters "attacked security forces" using live ammunition and bird shot.
The protesters said demonstrators were peaceful and that they were attacked during dawn prayers outside the Republican Guard headquarters.
The suspects face charges of manslaughter, voluntary manslaughter, thuggery, possession of unlicensed firearms, illegal possession of ammunition and weapons and undermining general security with the intent to terrorize.
Egypt's main liberal opposition group and the Muslim Brotherhood both have rejected the military-backed interim leadership's elections timetable.
The rival groups' rejection came as interim President Adly Mansour named former Deputy Prime Minister and Finance Minister Hazem al-Beblawi as prime minister and appointed liberal opposition chief and Nobel Peace laureate Mohamed ElBaradei as vice president for foreign relations.
The National Salvation Front -- led by ElBaradei until his appointment -- demanded more changes to Mansour's transition plan, presented as a "road map" to amending the Islamist-drafted constitution and holding new parliamentary and presidential elections within six months.
"The National Salvation Front announces its rejection of the constitutional decree," the group said in a statement, explaining it was not consulted on the document vital to Egypt's political transition.
The coalition of more than 35 groups opposed to Morsi, ousted as president a week ago, did not elaborate further.
The Brotherhood, pressing for the immediate reinstatement of Morsi, also rejected the Mansour decree.
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