Egypt's prosecutor general on Monday ordered the arrest of five young opposition activists on charges of inciting violence, following clashes last week in Cairo, state news agency MENA reported.
The order came as a warning from President Mohamed Morsi that political figures could be sanctioned if found to have stirred up the unrest drew the ire of the opposition and newspapers.
MENA said the five -- Alaa Abdel Fattah, Ahmed Duma, Karim el-Shaer, Hazem Abdel Azim et Ahmed Eid -- also had their names added to a black list barring them from travel abroad.
On Sunday, Morsi warned:"If investigations prove that certain political figures are implicated, the necessary measures will be taken against them, whatever their status."
The warning followed violent clashes last Friday in Cairo between pro-opposition demonstrators and Islamists from Morsi's Muslim Brotherhood movement that left 160 people injured.
The two sides have traded blame for the violence, against the backdrop of high political tensions which divide Egypt two years after the revolution that ousted president Hosni Mubarak.
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"We can expect the worst. Morsi's threat signals the death of the state of law. They show that he is president only of the Muslim Brotherhood," charged Khaled Daud, spokesman of the National Salvation Front opposition coalition.
"President Morsi always swings into action when the Muslim Brotherhood is under pressure, but he does nothing when his supporters attack the opposition," according to Abdel Ghafar Shokr, an NSF leader.
Al-Watan newspaper spoke of "a threat to the opposition," while Al-Masry Al-Youm accused the president of preparing "exceptional measures" against the opposition and of trying to intimidate the media.
The Brotherhood's lawyer Abdelmoneim Abdel Maksud, meanwhile, said he has filed suits against 169 people, including known political figures, over last week's violence, without giving names.
On Monday, hundreds of Islamists, mostly Salafists hardline Muslims, kept up a protest action in front of Media City, a complex of studios and private television stations on the outskirts of Cairo.
Several employees in Media City have said they were attacked or intimidated by the protesters, who accuse the private media of bias against Islamists and of having incited Friday's unrest.
Officials on Monday condemned the protesters' actions.