TONY G. GABRIEL
CAIRO (AP) -- Egyptian security forces stormed a Cairo mosque Saturday 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 overnight after violent clashes killed 173 people.
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 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 Salafi 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 official spoke on condition of anonymity as he wasn't authorized to brief journalists about the arrest.
The Egyptian government meanwhile announced it had begun deliberations on whether to ban the Brotherhood, a long-outlawed organization 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 decades-long power struggle between the state and the Brotherhood.
For more than a month since the July 3 military overthrow of Morsi, Brotherhood members and supporters have attacked and torched scores of police stations and churches, in retaliation. Shops and houses of Christians have also 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 Mubarak's rule in the 1990s which only strengthened security agencies and ended up with thousands of Islamic fundamentalists in prisons.
The unrest in Egypt has raised international concerns over the country's stability and prompted U.N. Secretary General Ban Ki-Moon to condemn in a statement on Saturday both "violent protests" in reference to Brotherhood's rallies and the authorities' "excessive use of force."
Ban also noted, in an apparent rebuff of Brotherhood demands to reinstate Morsi, that the "political clocks move only forward, not backward" and urged "maximum restraint and shift immediately to de-escalation."
Former President Jimmy Carter expressed deep concern over the violence, saying it is "rapidly eroding the chances for dialogue and a road to reconciliation." Carter added that he is "especially concerned that Egyptians are arming themselves and engaging in inter-communal violence."
In Cairo, the assault on the al-Fath Mosque began on Friday when pro-Morsi protesters and armed men fled into the worship center 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 Saturday, security forces and armored personnel carriers had surrounded the mosque and it appeared that military-led negotiations might defuse the standoff.
A post on the Facebook page of the army spokesman, Col. 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.
A Muslim cleric, Sheik Abdel-Hafiz el-Maslami, told The Associated Press that people were afraid to leave the mosque out of fear of detention or being assaulted by the crowd outside. He said there were armed men inside the mosque at one point but protesters had forced them out.
"We lost control over things," the cleric said. "There were men with arms in the mosque who were forced out of the mosque but we can't control things here."
He said there were ongoing negotiations with the military to enable the protesters to safely leave. State television showed small groups emerging from the mosque by late Saturday morning.
However, local journalist Shaimaa Awad who was trapped in the mosque with the Islamists said the talks failed after three women were detained by the military after agreeing to get out early Saturday morning.
An AP reporter said that thousands of anti-Islamist protesters rallied outside the mosque, chanting: "God take revenge on Morsi and those standing behind him!"