Qasr El-Nil prosecution ordered Saturday the detention of April 6 Youth Movement founder Ahmed Maher for a day on charges of assaulting Brigadier-General Emad Tahoun.
Maher who denied the accusation of assaulting Tahoun and stealing his walkie talkie, will remain in police custody until the police officer gives his testimony Sunday.
The former head of the April 6 Youth Movement is also accused of blocking a road and calling last Tuesday's protest without requesting authoritisation, as stipulated by the newly-issued protest law.
Maher, however, told the prosecution that the protest, which was held in front of the Shura Council and against an article in the constitution allowing military trials for civilians, was peaceful and that security forces initiated an assault on protesters, sexually harassed women protesters, and forcefully arrested some.
Two demonstrations on Tuesday — one commemorating a protester killed last year, and the other a rally against military trials for civilians — were dispersed promptly by police, with dozens of demonstrators arrested.
A group of female detainees were released on a desert highway after being allegedly beaten and sexually assaulted by police. Some 24 male protesters remain in custody and were slammed Friday with 15 days in detention pending investigations.
Arrest warrants were issued last week for Maher and activist Alaa Abdel-Fattah, accusing them of calling for Tuesday's demonstrations without taking the necessary steps required by the new law on protests.
Abdel-Fattah was ordered Friday detained for four days pending investigations.
Six female activists who are part of the No to Military Trials group presented themselves to the prosecution office Wednesday and stated that they were the organisers of the protest.
No charges were brought against them, and they were not detained.
Egypt's new protest law, issued last Sunday by Interim President Adly Mansour, requires protest organisers to notify authorities three days in advance of a protest's aims and demands, imposing heavy jail terms and fines on individuals who break the law.