Offices of the Brotherhood Freedom and Justice political party were set ablaze in Alexandria and reportedly in other cities. Pro- and anti-Morsi demonstrators clashed in Cairo and in towns across southern Egypt.
The unrest highlighted the anger that arose after Morsi's decision on Thursday to free himself from judicial oversight. With no new constitution or parliament, the president holds wide executive and legislative powers.
"Morsi is ignorant. He will burn down the country," protesters chanted in Cairo.
Police fired tear gas at rock-throwing youths near Tahrir Square, where tens of thousands of protesters, led by Nobel laureate Mohamed ElBaradei and other opposition leaders, gathered.
Miles away in north Cairo, thousands of Brotherhood members and Morsi supporters demonstrated at the presidential palace.
"What I am working to achieve is political and economic stability. This is what I want," Morsi told his followers at the palace. "I am not worried about the presence of opposition. I am careful to allow a strong opposition that will strictly monitor me. My decisions were aimed at preserving our nation, our people, and the revolution."
Morsi, who was elected after the overthrow of President Hosni Mubarak, is strategizing to weaken the courts and Mubarak-era judges that he contends have created gridlock and slowed the transition to democracy. The Supreme Constitutional Court this year dissolved the Islamist-led parliament and has been reviewing a case that could possibly disband the assembly writing a new constitution. That body is dominated by Islamists and Morsi's decree granted the assembly immunity from court decisions.
Protesters were not convinced.
"The state is crumbling. The law is being completely sidestepped. We are now a lawless country," said Nermin Tahoon, a protester in Tahrir. "Morsi disguised the revolution's demands into a twisted package so he could assume all power. Since when was he a revolutionary? He's barely a reformist. He simply wants power for him and his followers."
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