The death toll in violence on Monday (July 8) at the Cairo headquarters of the Republican Guard rose to 42, Egyptian state television said, after the Muslim Brotherhood accused the security forces of attacking protesters.
The Egyptian military said "a terrorist group" had tried to storm the building. One army officer was killed and 40 wounded, the military said.
State television reported that an additional 322 people were wounded in what it described as an attempt to storm the Republican Guard's headquarters.
Bodies were taken to Nasser City Hospital. One injured man said he was hit by a tear gas canister.
The bloodshed deepened Egypt's political crisis, escalating the struggle between the army, which overthrew Morsi last Wednesday after mass demonstrations demanding his resignation, and the Brotherhood, which has denounced what it called a coup.
The Muslim Brotherhood called on Egyptians to rise up against those who "want to steal" the revolution, a statement by its political wing said on Monday.
Talks on forming a new government were already in trouble before Monday's shooting, after the Nour party rejected two liberal-minded candidates for prime minister proposed by interim head of state Adli Mansour.
Nour, Egypt's second biggest Islamist party, which is vital to give the new authorities a veneer of Islamist backing, said it had withdrawn from the negotiations in protest at what it called the "massacre at the Republican Guard (compound)".
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