Political activist Alaa Abdel-Fattah has been remanded in custody for four days pending a probe by the prosecution into charges of protesting outside the Shura Council without prior permission.
Under a new law, protesters should seek a permission from the authorities to stage any rally.
Abdel-Fattah faces charges of assembling, protesting and organizing a protest without informing the authorities concerned.
The prosecution also ordered that Abdel-Fattah be medically examined to determine what wounds he had sustained during the protest.
Abdel-Fattah denied all accusations leveled against him, insisting the protest remained peaceful. He accused police officers of hitting him on the head while arresting him.