CAIRO (AP) - Egypt's Muslim Brotherhood says a son of its spiritual leader was killed during fierce clashes in downtown Cairo, as hundreds of Islamist supporters of the country's ousted president remained barricaded inside a mosque.

The group's political arm said on its official website on Saturday that Mohammed Badei's son Ammar was killed on Friday. That is when the Muslim Brotherhood took to the streets in a "Day of Rage" - ignited by anger at security forces over clearing two sit-in camps earlier in the week, leaving hundreds dead.

Meanwhile, hundreds remained inside the al-Fatah mosque in Cairo on Saturday morning after barricading themselves inside overnight. A Muslim cleric there said there were ongoing negotiations with the military to have protesters safely leave.