Egyptian riot police deployed on Saturday near President Mohamed Morsi's palace as his administration rushed to contain fallout from footage of police beating a naked man during the deadly overnight clashes.
In Cairo's Tahrir Square, protesters stoned Prime Minister Hisham Qandil's motorcade when the premier tried to visit after separate overnight clashes nearby between protesters and police, Egypt's Dream Live television channel reported.
A 23-year-old was shot dead in late Friday's clashes as police used birdshot and tear gas on demonstrators who targeted the northern Cairo palace in rallies against the Islamist president, a senior medical official said.
Ninety-one people were also injured, the official added, while the interior ministry reported 15 of its men wounded by birdshot.
Police said they made 20 arrests, and were filmed on television beating and dragging a naked man to an armoured vehicle, outraging Morsi's critics, who compared the incident to practices under deposed president Hosni Mubarak.
The opposition National Salvation Front is to meet later on Saturday to review its strategy after the clashes, which followed its call for people to take to the streets.
The NSF on Saturday called for Interior Minister Mohammed Ibrahim to resign over the beating of the naked man, which triggered an outpouring of condemnation on social media websites.
"The horrible and degrading images showing the central security officers and police beating and dragging a naked man near the presidential palace should lead to the interior minister's immediate resignation," NSF spokesman Khaled Dawoud said.
Ibrahim has ordered a probe to "hold accountable" the policemen who beat the man, his office said. Prosecutors claim the man, a 50-year-old construction painter now held in a police hospital, was found carrying petrol bombs.
The presidency said it "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."
A statement added that it would follow the interior ministry's investigation, of what it called an "isolated act."
There was no sign of any protesters on Saturday, and debris-littered streets around the presidential palace reopened to traffic.
The smell of tear gas lingered near the palace, its outer wall scrawled with graffiti including "Topple the regime" and "Freedom."
In iconic Tahrir Square, protesters threw stones and bottles at Qandil's motorcade in the morning, Dream Live television said.
The premier said in a statement that he was "confronted by youths and troublemakers" and he "preferred to avoid a confrontation between them and security personnel."
The presidency said security forces would deal with violent protests with "utmost decisiveness" and that it would hold opposition groups found to have incited the clashes "politically accountable."
Morsi's Facebook page said the protesters sparked the violence by trying to break into the palace.
The opposition, which accuses Morsi of betraying the revolution that toppled Mubarak two years ago, distanced itself from the violence and urged demonstrators to exercise "utmost restraint."
But hours before the violence erupted, NSF leader and Nobel Peace laureate Mohamed ElBaradei suggested unrest would persist if Morsi kept sidelining his opponents.
"Writing on wall: violence and chaos will continue until Morsi and co. listen to people's demands: new government, democratic constitution, independent judiciary," he wrote on Twitter.
The NSF joined rival Islamists on Thursday in condemning violence and supporting efforts for a national dialogue, but insisted on a unity government and the amendment of the Islamist-drafted constitution that has polarised the nation.
People took to the streets in several cities on Friday in a show of opposition to Morsi and his Muslim Brotherhood after deadly unrest swept Egypt last week in the worst violence since Morsi was elected in June.
Nearly 60 people died in those clashes, mostly in Port Said. Violence erupted there after 21 local supporters of a football club were sentenced to death a week ago over the killings of 74 people during post-match violence.
The crisis has sapped Morsi's popularity and complicated negotiations for a crucial $4.8-billion IMF loan that could help bail out the teetering economy.