Egypt's public prosecution ordered on Tuesday the detention for 15 days of a controversial ultra-conservative preacher over violence-related charges.
Mahmoud Shaaban was arrested on Tuesday for allegedly inciting violent and terrorist acts, threatening social peace and calling for nationwide Islamist protests on Friday, a judicial source said.
Early in 2013, Shaaban was arrested and later released on bail under deposed president Mohamed Morsi, after issuing a fatwa sanctioning the killing of opposition politicians.
Shaaban was a theology professor at Al-Azhar University, the highest seat of Sunni Islam, but was suspended earlier this month over allegations of "inciting violence" at the university -- a hub of Islamist protests against the authorities.
A video was published on social media websites last month of a speech by Shaaban in which he referred to ISIS as fellow Muslims who had "made mistakes and whom we are obliged to guide and mentor."