It was not immediately clear why police did not stop the protesters from reaching Tahrir, a 30-minute journey on foot from the university campus on the west bank of the River Nile. There was no police presence outside the campus either.
Jubilant Islamist students knelt down and offered a prayer of thanks as their march drew closer to Tahrir. Once there, they chanted slogans against the military and police and flashed the four-finger sign that commemorates the death of hundreds of Morsi supporters by security forces since a military coup ousted the Islamist president on July 3.
Morsi's supporters immediately relayed the news on social networks, calling on others to join them quickly and suggesting that camping out indefinitely in the iconic square would eventually topple the military-backed government.
Also on Sunday, Egyptian authorities ordered the release from police custody of prominent activist Ahmed Maher, founder of the revolutionary April 6 Movement, a main player in the 2011 revolt against Mubarak. Prosecutors, however, extended by 15 days the detention of another iconic figure from the 2011 uprising — Alaa Abdel-Fattah.
Both men face accusations related to intensely publicized clashes on Tuesday between police and demonstrators protesting a clause in a new draft constitution enshrining the trial in some cases of civilians before military tribunals. Both Maher and Abdel-Fattah are accused of assaulting policemen during the protest in downtown Cairo.
Maher surrendered to police on Saturday. Abdel-Fattah was arrested at his home two days earlier.
Human Rights Watch on Sunday urged Egypt's military-backed government to immediately release from detention the five presidential aides. The New York-based advocacy group said in a statement that the five have been held at an undisclosed destination since July 3.
The five advisers still in detention are among nine presidential aides detained in July along with Morsi. The other four have been transferred to regular prisons and are facing criminal charges.
"What kind of roadmap is this where a military-backed government can brazenly disappear former presidential aides for 150 days without any explanation?" said Sarah Leah Whitson, Middle East and North Africa director at Human Rights Watch. She was referring to the roadmap for a post-coup return to democracy announced by military chief Gen. Abdel-Fattah el-Sissi when he toppled Morsi, Egypt's first freely elected president.
"Forcibly disappearing people for months on end doesn't inspire confidence that this government intends to follow the rule of law," she added. "The prolonged enforced disappearance of anyone is a crime, pure and simple. The Egyptian authorities should immediately free them unconditionally."
According to HRW, the five still held at a secret location are: Essam el-Haddad, Morsi's top foreign policy adviser, Ayman Ali, who advised him on the affairs of Egyptian expatriates, aide Ayman el-Serafy, media adviser Abdel-Meguid el-Meshaly and foreign affairs aide Khaled el-Qazzaz.
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