Military spokesman Ahmed Aly said in a press conference on Monday afternoon that army and police forces protecting the Republican Guard headquarters were attacked on Monday by armed groups.
According to Aly, pro-Morsi protesters, who have been gathering outside the Republican Guard headquarters for days, used live ammunition and bird shots against security personnel.
He added that at the time of the attack, another group was shooting from atop a building on Al-Tayaran street, where the military facility is located.
"A colleague is in Maadi hospital undergoing a four-hour surgery; he was shot with live ammunition in the head, which caused his skull to fracture," said Aly. Aly said that the officer's injury proves that there was firing from building rooftops.
The military spokesman went on to accuse "certain factions" of inciting violence, as a video of Brotherhood-affiliated preacher Safwat Hegazy was screened in the background.The video, which has gone viral on social networks, contains a threat of "escalation" from Morsi supporters if the former president is not reinstated.
"Interfering with Egypt's national security will not be allowed," Aly also said.
At least 51 people were killed and 435 injured in clashes on Monday morning between Morsi supporters and the army.  The Muslim Brotherhood said a peaceful pro-Morsi sit-in was attacked by the military during dawn prayers, while the military stated that an "armed terrorist group" attacked the Republic Guard headquarters, leading to the deaths.
The Muslim Brotherhood has been leading a sit-in for several days in front of the Republican Guard headquarters to demand the return of deposed president Mohamed Morsi.
Initial investigations by the prosecution found remains of Molotov cocktails and bullet and birdshot casings at the site of the clashes.