Sporadic clashes broke out overnight between protesters demanding the ouster of Egypt's Islamist President Mohamed Morsi and security forces outside the presidential palace, witnesses said on Sunday.
There were no reports of casualties from the confrontations which follow violent clashes on Friday outside the presidential palace that left one person dead.
Late on Saturday several hundred mostly young protesters again gathered outside the compound and threw stones and petrol bombs at its walls, an AFP correspondent said.
One protester said they were there to pay homage to the young man killed on Friday, and they chanted "Leave!" and "The people want the regime to fall!" -- slogans used two years earlier against ousted veteran president Hosni Mubarak.
Security forces deployed outside the palace grounds fired tear gas overnight when protesters tried to storm one of the gates, the witnesses said.
The head of the military's Republican Guards, tasked with protecting the presidency, said his troops would ignore "provocation" from protesters, the official MENA news agency reported.
The main opposition National Salvation Front (NSF), meanwhile, called for the resignation of Interior Minister Mohammed Ibrahim after a video showing a naked man being beaten by police during Friday's protest went viral on the Internet.
The beating was "an inhumane spectacle... no less ugly than the killings of martyrs, which is considered a continuation of the security force's programme of excessive force," the opposition bloc said.
Ibrahim ordered a probe into the incident and said he would resign if "that's what the people want," his office said.
The presidency also scrambled to contain fallout from the footage.
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A statement said the presidency was "pained by the shocking footage of some policemen treating a protester in a manner that does not accord with human dignity and human rights" but described the incident as an "isolated act."
Prosecutors say Hamed Saber, a 50-year-old construction painter, was found carrying petrol bombs.
Saber said on television that he had been set upon and stripped by protesters and that the police had saved him, but his daughter Randa disputed the account and said on television: "He's lying; he's scared."
A nephew of Saber added: "He is lying because there is a lot of pressure on him."
On Sunday, calm prevailed in Cairo but the widening gap between the presidency and the opposition was evident.
The Freedom and Justice and Party, the political arm of the Muslim Brotherhood from which Morsi hails, accused the NSF, led by failed presidential candidates, of trying to take the presidency by force.
"Being a witness to violence and the armed militias of the NSF, people now know the assailants trying to take over the presidency by force after being defeated in the vote," wrote a commentator in the party's newspaper.
Meanwhile, Egypt's top court the Supreme Constitutional Court on Sunday postponed a ruling until March 3 on the legality of the Islamist-dominated commission that drafted a contested new constitution, state media reported.
The legality of the panel that drafted the constitution is at the heart of Egypt’s worst political crisis since the overthrow nearly two years ago of former president Hosni Mubarak.
The charter has divided Egypt, pitting Morsi and his backers against the opposition which includes secularists, leftists and Christians as well as Muslims.
Since the start of the new wave of violence in Egypt on January 24, the eve of the second anniversary of the uprising that ousted Mubarak, nearly 60 people have been killed in the country.