According to the local media, a decree by Mansour made public on Monday said there would be a panel to review all the controversial constitutional provisions which were approved under President Mohamed Morsi, whose removal from office by the military has triggered a major crisis in the North African country.
The revised constitution would be put to a referendum with parliamentary elections within two months to fix the date for a presidential vote.
The decree was released on a tension-filled day with angry supporters of the Islamist Muslim Brotherhood continuing their sit-in on the streets and its leadership declaring an “uprising” following the killing of dozens of its members by the military at dawn on Monday.
At least 51 people have been killed and 435 injured, according to official count, when soldiers opened fire on a crowd of mostly members of the Brotherhood near the Presidential Guard barracks where they believe ousted President Mohamed Morsi is being kept.
Mansour has called for restraint and promised investigations into the killings.
Local media reports quoted an official of the Ministry of Health, Khaled al-Khaib, to have given the figures.
The bloodiest day, since Morsi was removed from power last Wednesday, has seen the North African country being pushed to the brink, as it remains dangerously split down the middle.
Army spokesman Col. Ahmed Mohammed Ali and Interior Ministry Spokesman Hani Abdel-Latif told a news conference that the protesters, who also included members of the Muslim Brotherhood that helped to propel Morsi to power last year, attacked people protecting the barracks with guns, bombs and rocks.
The claim could not be independently verified.
The official version says the attack on the barracks led to the death of three people – one soldier and two policemen.
Muslim Brotherhood says the army opened fire on its members who were preparing for dawn prayers without provocation, but the army says a group of “terrorists” tried to storm the barracks.
Angry leaders of the Muslim Brotherhood have declared it a “massacre” and called for an “uprising” raising fears of more clashes with the military and anti-Morsi supporters, whose loud demand for the president’s departure apparently accelerated the intervention of the military last Wednesday night.
Adly Mansour, the man who has been sworn in as Egypt’s interim president, has called for restraint in the divided North African country.
Although he has promised an investigation, this has not appeased the pro-Morsi supporters who want nothing but his reinstatement.
The developments are pushing efforts to form a broad-based government and organise elections against a steep hill.
The second largest Islamic party in Egypt, Salafist Nour, which was cooperating with the military, has pulled out after also describing Monday morning’s shooting as a “massacre”.
The army has closed down the headquarters of Morsi’s Freedom and Justice Party saying it had found arms in the building.
The Egyptian military Chief, Gen.Abdel Fattah al-Sisi, in a nationwide television broadcast on Wednesday night, announced the removal of Morsi from power and suspension of the constitution.