A Cairo prosecution office has ordered the detention of Islamic sheikh and TV presenter Abdullah Badr and Salafist activist Gamal Saber for 15 days pending investigations into charges of inciting murder at the presidential palace in December 2012.
Both men are already in jail on other charges.
The two men are accused of inciting the killing of protesters at the Ittihadeya presidential palace and attempted murder. They were also accused of belonging to a "militant terrorist" group, illegally possessing arms and ammunition, and spreading chaos in society.
At least ten people were killed and over 600 injured during clashes between supporters and opponents of former president Mohamed Morsi outside the Ittihadeya presidential palace in Cairo's Heliopolis district last December. Opponents of Morsi were protesting against his 22 November 2012 constitutional declaration which extended his powers and shielded them from judicial oversight.
Several Islamists are currently facing investigations into charges of involvement in the same clashes, including Rifaa El-Tahtawi, Morsi's former chief of staff, and a number of his aides.
Badr, a controversial fiery preacher, was sentenced to five years in prison on 24 June for broadcasting fabricated images of Egyptian actress Elham Shahin on his television programme.
Similarly, Saber, the coordinator of "Lazem Hazem," a group supporting former Salafist presidential runner Hazem Salah Abu-Ismail, is already in jail pending investigations into his alleged involvement in clashes in Cairo's Shubra district in March that killed three and left dozens injured.
The Shubra clashes began with a personal fight in which Saber and his sons became involved. Saber's sons, Ahmed and Abdel-Rahman, are facing charges of attempted murder, possession of weapons, resisting authorities and thuggery in the Shubra clashes. The two young men denied all charges and alleged they were only watching the fight from afar.