CAIRO, Egypt (CNN) -
A wave of fresh clashes erupted in Egypt on Sunday as resentment over the president's new powers and support for him continue to divide the country.
The latest clashes broke out between protesters and security forces on the outskirts of Tahrir Square, in Cairo, Egypt's state-run Nile TV reported.
The unrest may be a prelude to dueling demonstrations scheduled for later this week.
The sides are divided over Egyptian President Mohamed Morsy and the Islamist movement that he once led. On Thursday, he announced that courts could not overturn any decree or law he has issued since taking office in June and, beyond that, in the six months until a new constitution is finalized, his spokesman said on state-run TV.
The president also fired Egypt's prosecutor general, who has been criticized for the insufficient prosecutions of those suspected in demonstrators' deaths in 2011.
The moves sparked widespread protests.
The opposition has called for an open-ended sit-in at Cairo's central Tahrir Square "to defend the revolution and the Egyptian state," according to state-run EGYNews. It is planning a major protest Tuesday.
Meanwhile, the Muslim Brotherhood, the movement Morsy once led, has said it will stage nationwide demonstrations starting Sunday to back the president's plans. It also announced a "Million Man" demonstration Tuesday at Abdeen Square in Cairo to support Morsy.
Sunday also marked the first day trading resumed on the Egyptian stock market since Morsy's power consolidation.
By midday local time, stocks had plunged by about 10%.
Tahrir Square was the focal point of a popular uprising last year that forced longtime leader Hosni Mubarak out of office.
Just as they did during 2011, white tents dotted Tahrir Square early Sunday. In previous days, clashes between protesters and police were reported in the capital, the port city of Alexandria and elsewhere around the North African nation.
Since Morsy made his announcement Thursday, at least 261 people have been injured in clashes in Cairo and elsewhere, according to EGYNews, which cited the Health Ministry. EGYNews gave no breakdown as to who was hurt.
Interior Ministry spokesman Alaa Mahmoud said 128 police officers were injured in clashes nationwide.
On Saturday, Egypt's highest judicial body joined protesters in lambasting the country's president for issuing a decree disabling the courts and giving him unchecked power.
The Supreme Judicial Council called the decree an "unprecedented attack on the independence of the judicial branch," state-run media reported.
Dozens of protesters, some throwing rocks, faced off in central Cairo with police, who fired tear gas canisters at them.
Egyptian state TV reported clashes outside the judicial building in Cairo between opponents and supporters of the government. Clashes continued between protesters and security forces, with police firing tear gas and warning shots in the air near the Interior Ministry.
Ministry spokesman Mahmoud said hundreds of Morsy supporters and members of the Muslim Brotherhood attempted to storm the building, but riot police stopped them.
The protesters congregated at the entrance of the judicial building. That's where the leadership of the Egypt Judges Club, an association of judges from across the country, was meeting with former Prosecutor General Abdel-Meguid Mahmoud.
The judges and Mahmoud vehemently oppose Morsy's actions.
The general assembly of the judges' club called for a nationwide strike in all courts and prosecution offices to protest the president's move, state-run Nile TV reported.
Judges in Alexandria and Damanhour said they are putting all court hearings on hold until further notice.
Yet other judges offered support for Morsy. The Judges for Egypt movement, a nongovernmental organization, denounced any call for a strike, according to state-run TV.
Calling for calm and dialogue, the U.S. State Department expressed concern Friday about the recent developments in Egypt, saying, "One of the aspirations of the revolution was to ensure that power would not be overly concentrated in the hands of any one person or institution."
Last week, Morsy insisted his actions are in the interests of the Egyptian people.
"I have dedicated myself and my life for democracy and freedom," he told hundreds of supporters outside the presidential palace in Cairo. "The steps I took are meant to achieve political and social stability."
Amid the turmoil in Cairo, a bomb exploded at a Central Security Forces camp in North Sinai province, a security official said.
North Sinai security head Gen. Sameh Bishady said no soldiers were at the camp in el-Arish, and no casualties were reported. But it was the second explosion in the same area in less than 24 hours.