The National Salvation Front, the top opposition political group during Morsi's presidency and a key member of the coalition that worked with the military in his removal, criticized the moves, saying, "We totally reject excluding any party, particularly political Islamic groups."
The Front has proposed one of its top leaders, Mohammed ElBaradei, to become prime minister of the interim Cabinet, a post that will hold strong powers since Mansour's presidency post is considered symbolic. ElBaradei, a Nobel Peace laureate who once headed the U.N. nuclear watchdog agency, is considered Egypt's top reform advocate.
"Reconciliation is the name of the game, including the Muslim Brotherhood. We need to be inclusive," Munir Fakhry Abdel-Nour, a leading member of the group, told The Associated Press. "The detentions are a mistake."
He said the arrests appeared to be prompted by security officials' fears over possible calls for violence by Brotherhood leaders. There may be complaints against certain individuals in the Brotherhood "but they don't justify the detention," he said, predicting they will be released in the coming days.
Abdel-Nour said the Front intends to ensure the military has no role in politics. He added that the Front is hoping for the backing of ultraconservative Salafis for ElBaradei's bid for prime minister. Some Salafi factions have sided with the new leadership. He noted that the constitution was not outright canceled, in a gesture to Salafis.
Morsi has been under detention in an unknown location since Wednesday night, and at least a dozen of his top aides and advisers have been under what is described as "house arrest," though their locations are also unknown.
Besides the Brotherhood's top leader, General Guide Mohammed Badie, security officials have also arrested his predecessor, Mahdi Akef, and one of his two deputies, Rashad Bayoumi, as well as Saad el-Katatni, head of the Brotherhood's Freedom and Justice Party, and ultraconservative Salafi figure Hazem Abu Ismail, who has a considerable street following.
Authorities have also issued a wanted list for more than 200 Brotherhood members and leaders of other Islamist groups. Among them is Khairat el-Shater, another deputy of the general guide who is widely considered the most powerful figure in the Brotherhood.
The arrest of Badie was a dramatic step, since even Mubarak and his predecessors had been reluctant to move against the group's top leader. The ranks of Brotherhood members across the country swear a strict oath of unquestioning allegiance to the general guide, vowing to "hear and obey." It has been decades since any Brotherhood general guide was put in a prison.
Badie and el-Shater were widely believed by the opposition to be the real power in Egypt during Morsi's tenure. Badie was arrested late Wednesday from a villa where he had been staying in the Mediterranean coastal city of Marsa Matrouh and flown by helicopter to Cairo, security officials said, speaking on condition of anonymity because they were not authorized to talk the press.
Mahmoud, the top prosecutor, said he was opening investigations into the killings of protesters during Morsi's rule. He ordered el-Katatni and Bayoumi questioned on allegations of instigating violence and killings, and put travel bans on 36 others, a sign they too could face prosecution. He also took steps toward releasing a prominent activist detained for insulting Morsi.
Mansour, the 67-year-old interim president, is a Mubarak appointee like nearly every judge. He had been the deputy head of the court for more than 20 years.
He was elevated to the chief justice position only three days ago, when his predecessor reached mandatory retirement age.
Mansour was among the judges who ruled against a political isolation law in 2012 that would have barred many Mubarak-era officials from politics. As a result, Mubarak's last prime minister, Ahmed Shafiq, was able to run against Morsi.
In his speech, Mansour said the massive street demonstrations "brought together everyone without discrimination or division," and were an "expression of the nation's conscience and an embodiment of its hopes and ambitions."
But he made no sign of outreach to the Brotherhood in his address. He suggested Morsi's election had been tainted, saying, "I look forward to parliamentary and presidential elections held with the genuine and authentic will of the people."
The revolution, he said, must continue so "we stop producing tyrants."