Egyptian prosecutors have ordered the detention of Salafist leader Hazem Salah Abu-Ismail for inciting the murder of anti-Morsi protesters.
The former presidential candidate was arrested at his home on Friday. He can be held for up to 15 days.
Abu-Ismail allegedly incited violence that led to the deaths of nine protesters in Giza.
He has been transferred to Tora prison, Al-Ahram Arabic news website reported.
Nationwide clashes since Mohamed Morsi's ouster on Wednesday have killed at least 37 people and injured over 1,400.
Earlier on Sunday, four senior Muslim Brotherhood leaders were arrested on charges of inciting the killing of anti-Morsi protesters outside the group's headquarters in Cairo on 30 June.
Nine people were reportedly killed by live ammunition at the Islamists group's headquarters before it was stormed, torched and ransacked.
Deputy Supreme Guide Khairat El-Shater, former supreme guide Mahdy Akef, deputy leader Rashad Bayoumi and Freedom and Justice Party (FJP) leader Saad El-Katatni will be held for 15 days.
A number of Islamist figures have been arrested or banned from leaving the country since Morsi's ouster.
Abu-Ismail was disqualified from the presidential race in June 2012 because his late mother was a US citizen.