Egyptian authorities have arrested the brother of al-Qaeda chief Ayman al-Zawahri, security officials said.
Mohammed al-Zawahri, leader of a Salafist group, was detained at a checkpoint in Giza, the city across the Nile from Cairo.
Mohammed al-Zawahri's group espouses a hardline ideology but was not clandestine prior to the military takeover on July 3.
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He was allied with ousted President Mohamed Morsi, whose supporters are now taking to the streets to protest the killings of its supporters in a security crackdown last week.
The official news agency, MENA, confirmed the arrest.
Authorities said earlier that Mohammed al-Zawahri had commanded fighters in Sinai Peninsula.
He was detained as part of a round up of more than than 1,000 Islamists in the country. The round up, announced by the authorities, was conducted after Friday's protests.
Mohammed al-Zawahiri had been seen in Cairo in January at protests outside the French Embassy by hundreds of Salafists against the French military campaign in Mali.