Egyptian police arrested the brother of Al Qaeda chief Ayman al-Zawahri on Saturday, as officials say he planned to bring in armed groups to support Morsi demonstrators holed up inside a mosque.
An official said Saturday that Mohammed al-Zawahri, leader of the ultraconservative Jihadi Salafist group, was detained at a checkpoint in Giza, the city across the Nile from Cairo.
The official declined to give further details. He spoke anonymously as he was not authorized to speak to the press.
Mohammed Al-Zawahri's group espouses a hard-line ideology but was not clandestine prior to Egypt's July 3 coup. He was allied with ousted President Mohammed Morsi, an Islamist, whose supporters are now taking to the streets to protest the killings of its supporters in a security crackdown last week.
Authorities also said earlier that al-Zawahri had commanded insurgents in Sinai Peninsula.
Hundreds of Morsi supporters had gathered Saturday at the al-Fath mosque on Ramses Square, the building that Mohammed al-Zawahri is accused of trying to defend with armed groups.
Security forces later raided the mosque, fearing that the Muslim Brotherhood was attempting to create another protest camp.
At one point, troops exchanged gunfire with men shooting from a minaret of the mosque.
The Associated Press contributed to this report.