Senior Muslim Brotherhood leader Mohamed El-Beltagy was arrested Thursday in Giza governorate, Ahram Arabic website reported.
El-Beltagy was observed by the police for two days before his arrest in the rural area of Abo El-Namras in Giza.
He has been in hiding since the police's bloody crackdown on the pro-Morsi sit-in in Cairo's Rabaa Al-Adawiya on 14 August.
El-Beltagy's daughter, Asmaa, 17, died during the crackdown on 14 August.
On Wednesday, El-Beltagy appeared on Al-Jazeera channel in a pre-recorded video reiterating his condemnation of what he described as a military coup. In the video, he said that the Egyptian authorities have no evidence that the Brotherhood have engaged in any terrorist acts, and he urged detained members of the Brotherhood not to answer questions by investigators as authorities "lack legitimacy.”
El-Beltagy is known for stating that if ousted President Mohamed Morsi returns to office, militant attacks in Sinai Peninsula, ongoing since Morsi's ouster on 3 July, will stop, a statement that government officials point to as proof that the group is supporting terrorism.
The prosecution had previously charged El-Beltagy with a number of offences, including attempted murder and forming a "terrorist gang" at the pro-Morsi Rabaa Al-Adawiya protest camp.
El-Beltagy is scheduled to be investigated in connection both with violence in early August at the Republican Guards headquarters in which 51 pro-Morsi protesters were killed, and a separate incident in which police clashed with Rabaa Al-Adawiya protestors.
State news agency MENA also reported that ex-minister of manpower Khaled El-Azhary and Brotherhood senior figure Gamal El-Ashry were arrested with El-Beltagy.