A prominent Egyptian blogger has handed himself over to the authorities a day after being accused along with four others of inciting violence.
Alaa Abdel Fattah was cheered by a crowd as he entered the Cairo office of Prosecutor General Talaat Abdullah.
Mr Abdullah had ordered the five to be arrested, accusing them of inciting "aggression" against members of the Muslim Brotherhood last week.
Mr Abdel Fattah was questioned for some hours before being released.
It is not clear if he faces further questioning.
More than 100 people were injured when opposition activists attacked the Brotherhood's headquarters last Friday.
The Muslim Brotherhood dominates parliament and is the party of Islamist President Mohammed Morsi.
Egypt's secular opposition accuses President Morsi of seeking to usurp power - a charge he denies.
Mr Abdel Fattah arrived at the prosecutor's office on Tuesday with his wife and child and carrying a rucksack. He told the crowd that the rucksack was in case he was detained.
His supporters chanted: "Down, down with Morsi's rule."
Mr Abdel Fattah's mother, Layla Soueif, told state-owned Ahram Online that her son was acting to safeguard his family.
"Alaa is not going to co-operate with the authorities but he doesn't want to put his wife and child through the stress of the police turning up on his doorstep, so he has come of his own accord today," the Cairo University professor said outside the office.
Once inside the office Mr Abdel Fattah tweeted that he had refused to answer Mr Abdullah's questions.
"In general I refused to answer all the questions because of partiality of the prosecutor general," he posted.
The other four accused - Ahmed Douma, Karim El-Shaer, Hazem Abdel Azim and Ahmed Ghoneimi - stayed at home, Ahram Online reported.
On Monday, a statement from the prosecutor's office said the five were accused of inciting "aggression against people, the destruction of property and disturbing civil peace in the events that erupted during the protest in front of the Muslim Brotherhood's headquarters."
The Brotherhood has already filed a legal complaint against 169 people, including party leaders, whom it accused of involvement in the violence.
Mr Abdel Fattah played a prominent role in the protests that led to the overthrow of President Hosni Mubarak in 2011.
Egypt has been rocked by violent protests this year, leaving dozens dead and many more injured.