At least 42 people have been shot dead near a military barracks in Cairo, amid ongoing unrest following the removal of Egypt’s President Mohammed Morsi.
The Muslim Brotherhood says its members were staging a pro-Morsi sit-in at the barracks, where he is believed to be in detention, when they were fired on.
But the army said a “terrorist group” had tried to storm the barracks.
The office of interim president Adly Mansour expressed “deep sorrow” over the deaths and called for restraint.
In a statement, he too said there had been an attempt to storm the Presidential Guard barracks.
Mr Mansour ordered the formation of a judicial committee to investigate the clashes, and urged protesters not to approach the military or “vital installations”.