Egypt: Opposition Leader Named Interim PM Egypt's new president moved to assert his authority Saturday by naming a chief rival of ousted leader Mohammed Morsi as interim prime minister and holding crisis talks with security officials on efforts to reclaim control of the streets. The steps by the untested Adly Mansour, however, are likely to deepen the defiance by Islamist opponents who have turned parts of the Cairo into vigilante-guarded strongholds and have issued blood oaths to battle until Morsi is restored. After a night of clashes that claimed at least 36 lives, both sides appeared to be preparing for the possibility of more violence as Egypt's political unraveling increasingly left little room for middle ground or dialogue. In the eastern suburb of Nasr City - near the main rallying point for Morsi's Muslim Brotherhood - lines of fighters brandished homemade weapons and body armor at road blocks affixed with Morsi's picture. Next door in the relatively upscale Heliopolis district, people chanted against Morsi and honked car horns in appreciation of roadblocks manned by Egypt's military - whose snub of Morsi's authority earlier this week tipped the scales against Egypt's first elected leader. Mansour's decision to bring pro-reform leader and Nobel laureate Mohamed ElBaradei into the key government role of prime minister is also certain to help cement the loyalties of the anti-Morsi forces. The president planned to swear-in ElBaradei later Saturday, said Khaled Dawoud, an official with the main opposition National Salvation Front. ElBaradei, a former director of the U.N.'s nuclear watchdog agency, led the protests against President Hosni Mubarak during the Arab Spring uprising that ended his autocratic rule in February 2011. The revolution also opened the way for the political rise of the Muslim Brotherhood, which was long under pressure from Mubarak's Western-backed regime. Elections last year brought Morsi to the presidency, but ElBaradei remained a voice of dissent, once saying the Brotherhood lived "in a delusion" for thinking its members could manage the country on their own. Egypt's new president - chief justice of the country's constitutional court - is little-known in international circles. But the choice of the 71-year-old ElBaradei gives the administration and prominent global figure to make its case to Washington and other Western allies trying to reassess policies after what Morsi's backers have described as a "coup." Morsi remains under detention in an undisclosed location. Earlier, the president held talks with the army chief and interior minister in apparent attempts to work out strategies to contain another round of violence. Morsi's supporters have vowed to take to the streets until the toppled Islamist leader is reinstated. His opponents, meanwhile, have called for more mass rallies to defend what they call the "gains of June 30." "The people here and in all of Egypt's squares are ready for martyrdom to restore legitimacy," said Abdullah Shehatah, a senior leader of the Freedom and Justice Party, the Brotherhood's political arm. Speaking at the main sit-in site of Morsi supporters in Cairo, he said: "This coup and all its institutions are illegal." There were no reports of major clashes in Egypt after dawn Saturday, following a night of street battles that added to an overall death toll of at least 75 in the past week.