Spokesman of the Muslim Brotherhood Gehad El-Haddad was arrested on Tuesday afternoon in an apartment in Cairo's Nasr City.
El-Haddad was apprehended along with Morsi-era governor of Qalyoubia Hossam Abu El-Bakr. He is accused of inciting violence and murder. He has been transferred to Tora prison located on the outskirts of Cairo.
El-Haddad is the son of Muslim Brotherhood leader and former presidential advisor for foreign affairs Essam El-Haddad, who has been held incommunicado along with president Mohamed Morsi following his ouster by the military amid nationwide protests on 3 July.
Prior to his arrest, El-Haddad was continuously publicising - via his twitter account - pro-Morsi rallies that have been taking place since the president's removal from office.
Hundreds of Muslim Brotherhood leaders and members have been arrested since the violent dispersal of pro-Morsi sit-ins at Rabaa Al-Adawiya and Al-Nahda squares on 14 August.
Haddad maintained a regular presence at the main pro-Morsi camp in Cairo's Rabaa Al-Adawyia, and has been tweeting from an undisclosed location since the end of the sit-ins.
Morsi, Brotherhood spiritual leader Mohamed Badie, and his second-in-command Khairat El-Shater all face charges related to the incitement of violence.