Egyptian security forces have stormed a Cairo mosque after a heavy exchange of gunfire with armed men shooting down from a minaret, rounding up hundreds of supporters of the country's ousted president who had sought refuge there after violent clashes killed 173.
The raid on the al-Fath mosque on Ramses Square was prompted by fears that deposed president Mohammed Morsi's group, the Muslim Brotherhood, again planned to set up a sit-in, security officials said, similar to those that were broken up on Wednesday in assaults that killed hundreds of people.
The arrest of the brother of al Qaida chief Ayman al-Zawahri came in connection to the raid on the mosque. Officials said that he planned to bring in armed groups to provide support to those holed up inside the mosque. Mohammed al-Zawahri, a Morsi ally, is the leader of the ultraconservative Jihadi Salafist group which espouses al Qaida's hardline ideology. He was detained at a checkpoint in Giza, the city across the Nile from Cairo, the official said.
The Egyptian government meanwhile announced it had begun deliberations on whether to ban the Brotherhood, a long-outlawed organisation that swept to power in the country's first democratic elections a year ago.
Such a ban - which authorities say is rooted in the group's use of violence - would be a repeat to the historic and decades-long power struggle between the state and the Brotherhood.
For more than a month since the July 3 military overthrow of Mr Morsi, Muslim Brotherhood members and supporters have attacked and torched scores of police stations and churches. Shops and houses of Christians have been targeted.
Such attacks spurred widespread public anger against the Brotherhood, giving the military-backed government popular backing to step up its campaign against the Islamist group. It reminded people of a decade-long Islamist insurgency against Mr Mubarak's rule in the 1990s which only strengthened security agencies and ended up with thousands of Islamic fundamentalists in prisons.
The assault on the al-Fath Mosque began on Friday, as pro-Morsi protesters and armed men fled into the worship centre to avoid angry vigilantes and arrest. They piled furniture in the mosque's entrance to block authorities and enraged anti-Morsi protesters from reaching them.
The mosque served as a field hospital and an open-air morgue as a Brotherhood-called day of protests descended into violence. By daybreak on Saturday, security forces and armoured personnel carriers had surrounded the mosque and it appeared that military-led negotiations might defuse the stand-off.
A post on the Facebook page of the army spokesman, Colonel Mohammed Ali, accused gunmen of firing from the mosque at nearby buildings, located on Ramses Square in central Cairo. The upper floors of a commercial building and blood bank towering over the square caught fire during the mayhem, with flames engulfing it for hours.