Dozens of Egypt's protesters have reportedly been killed by targeted shots to the head and chest, as the death toll from the country's latest civil strife rose to at least 50.
Supporters of the deposed Muslim Brotherhood president Mohammed Morsi stormed through Cairo and several other major cities over the weekend, as the military administration they oppose held commemoration rallies for the 40th anniversary of the 1973 Arab-Israeli war.
The commemorations were widely interpreted as a show of might by the Egyptian army, featuring displays of fighter jets and army helicopters.
Police told the BBC more than 200 people were arrested in Cairo during the disturbances, using tear gas and firing bullets into the air to calm the disturbances.
An Associated Press photographer reported that he had seen at least nine bodies, all of whom had been shot in the head, on the floor of a clinic in Dokki.
America's McClatchy Newspapers reported protesters died "overwhelmingly by gunshots to the head and chest."
Journalist Bel Trew, in Cairo, told Sky News the military had been expecting the unrest and described seeing "chaotic side street clashes with lots of gunfire and tear gas".
On Sunday, the Health Ministry reported 40 people killed in Cairo and four others killed in provinces south of Cairo, with more than 240 people injured. The death toll is now believed to have risen beyond 50 people across the country.
Earlier in the day, soldiers had barricaded entrances to central Tahrir Square with barbed wire and armored personnel vehicles. Metal detectors were installed at the entrances and demonstrators pouring into the square were searched by troops.
El-Sissi's predecessor, Field Marshal Hussein Tantawi, was among those attending the ceremony, making his first public appearance since Morsi removed him and his chief of staff, Sami Anan, in August last year.
Tantawi served Hosni Mubarak as defence minister for 20 years and took over the reins of the country when his mentor was ousted in a 2011 uprising.