Sporadic clashes broke out overnight between protesters demanding the ouster of Egypt's President Mohammed Morsi and security forces outside the presidential palace, witnesses told AFP 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, AFP reported.
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, 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 program of excessive force," the opposition bloc said, according to AFP.
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.
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."
The NSF on Saturday backed calls to oust Morsi, saying he should be prosecuted for "killings and torture," while urging Egyptians to stage peaceful protests.
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.