Clashes between Morsi supporters and opponents erupted outside a major mosque in the coastal city of Alexandria, with the two sides throwing stones and firing birdshot at each other. Police and army forces lobbed tear gas and deployed soldiers but were unable to break up the fighting, which killed two people and injured 24. Minor scuffles erupted in a Cairo neighborhood and in the Nile Delta city of Damietta with at least 18 injured, according to health officials.
The announcement of the case against Morsi, which is likely to pave the way to a formal indictment, was the first word on his legal status since the military deposed him on July 3. For more than three weeks, the Islamist leader has been held by the military in a secret location, incommunicado.
Supporters of Morsi denied the charges against him, calling them politically motivated but vowed to keep their protests peaceful.
On Friday, a spokesman for Morsi's Muslim Brotherhood said the move to prosecute Morsi showed "the complete bankruptcy of the leaders of the bloody coup."
Egyptians "reject the return of the dictatorial police state and all the repression, tyranny and theft it entails," Ahmed Aref said in a statement.
The accusations are connected to a prison break during the 2011 uprising against autocrat Hosni Mubarak in which gunmen attacked a prison northwest of Cairo, freeing prisoners including Morsi and around 30 other figures from his Muslim Brotherhood. The prosecutors allege Morsi and the Brotherhood worked with Hamas to carry out the break, in which 14 guards were killed.
The U.S. State Department spokeswoman Jen Psaki expressed deep concern about reports of Morsi's detention.
"I can't speak to the specific charges. But we do believe that it is important that there be a process to work toward his release," she said. "Clearly, this process should respect the personal security of him and take into account the volatile political situation in Egypt and that's where our focus is. We have conveyed publicly and privately that his personal security and treatment is of utmost importance."
Massive crowds, meanwhile, poured into main squares in Cairo and other cities in support of the military after the army chief Gen. Abdel-Fattah el-Sissi called for rallies. El-Sissi said days earlier he hoped for a giant public turnout to give him a mandate to stop "violence and terrorism," raising speculation he may be planning a crackdown on pro-Morsi protests.
At the same time, crowds of Islamist backers of Morsi massed at their own rallies, part of what the Brotherhood and its allies had previously said would be their biggest protests to date to demand the reinstatement of the president. El-Sissi's call days earlier may have been in part aimed to overwhelm the Islamist numbers in Friday's rallies, as each side tries to show the depth of its public support.
The rival shows of strength only deepen the country's divisions since Morsi's fall. Clashes and fistfights broke out between the rival camps in Alexandria, with two killed and 24 injured, according to health official Mohammed Abu Suleiman. Skirmishes also broke out in the Mediterranean coastal city of Damietta and a Cairo neighborhood that left a combined 18 injured, Health Ministry spokesman Khaled el-Khateeb said.
El-Sissi deposed Morsi after four days of giant protests by millions of Egyptians demanding the removal of the country's first freely elected president following months of political standoff between him and the largely secular opposition. Since then, Islamists have been holding sit-ins and rallies daily.
State media and pro-military private TV stations have been fiercely promoting the el-Sissi rallies, pumping up a nationalist fervor.
El-Sissi's portrait pervaded the crowds of tens of thousands in Cairo's central Tahrir Square: the smiling general in sunglasses on posters proclaiming "the love of the people," a combination photo of the general and a lion on lanyards hanging from people's necks, a picture of his face photoshopped into a 1-pound note of currency.
"The people, the source of all power, mandate the army and police to purge terrorism," read a giant banner stretched across one entrance to Tahrir. Three tanks guarded another street leading into the square, and helicopters swooped overhead.
Security was heavy after el-Sissi vowed to protect the rallies from attacks by rivals. Tanks guarded one entrance to Tahrir and police were stationed at other parts. "The people give their mandate," read signs touted by many in the crowd.
"The army is here to protect the people, they don't lie," said Ezzat Fahmi, a 38-year-old in the crowd. He said el-Sissi had to call Friday's rallies "so the entire world can see that the Egyptian people don't want the Brotherhood anymore."
Across town in eastern Cairo, thousands of pro-Morsi supporters packed a sit-in camp outside Rabaa al-Adawiyah mosque, chanting against el-Sissi and vowing to continue their push for Morsi's return.
The Muslim Brotherhood and allies, dubbing themselves as the anti-coup coalition, called the timing of the charges against Morsi "a malicious attempt to incite public opinion" and drag his supporters into violent protests. The statement vowed not to let that happen.
Maged Osman, a 25-year-old Morsi supporter, said el-Sissi's call for rival rallies won't silence his crowd.
"He is fueling more anger from one sector against another sector," he said.
Clashes have repeatedly erupted the past three weeks pitting Morsi supporters against his opponents or security forces. Each side blames the other for sparking violence, and people in both camps have been seen carrying weapons. On Friday, security forces in the Nile Delta city of Mahalla said they seized equipment and tools designed to create homemade guns, as well as guns and ammunition in an apartment. A security official said the tools and guns were seized following a tip that the products were being transported to pro-Morsi supporters. The official was speaking on condition of anonymity because he wasn't authorized to release the information.
It remains unclear what steps the military is planning after Friday's show of public strength. The most explosive step would be if it were to try to break up sit-ins by Islamists who have been camped out at locations in Cairo and other cities for weeks.
The military also could move to arrest more than a dozen Brotherhood figures who have arrest warrants against them. Or it could take firmer action to stop any sign of violence by Islamist protesters — though the Morsi camp says it is the one targeted by attacks. The word "wanted" in English was plastered across photos of a number of Brotherhood leaders and allies who are facing arrest warrants on the front page of the state-owned Al-Akhbar newspaper. Many of them are believed to be taking refuge in the Rabaa al-Adawiyah sit-in.
At the same time, Islamic militants have stepped up attacks on the army and police in the Sinai Peninsula. More than 180 people have been killed in Egypt since Morsi's fall.
The prosecutors' announcement on Morsi could signal a greater move to go after the Brotherhood in courts. Besides Morsi, five other senior figures from the group have been detained.
Senior Brotherhood official Essam el-Erian rejected the detention order, saying Morsi continues to enjoy immunity as the nation's "legitimate" president, and he can stand trial only as part of a constitutional process that allows that.
The detention order, he wrote on his official Facebook page, "lays bare the fascist nature of military rule ... our response will be with millions in peaceful rallies in the squares."
The MENA news agency said Morsi has now been formally detained for 15 days pending the completion of the investigation into the accusations. It did not say, however, whether he would now be moved now to a regular detention facility where he could receive family visits. The head of prison authorities, Maj. Gen. Mostafa Baz said he has not yet received orders for the transfer of Morsi to any of his facilities. His detention can be extended as the inquiry continues. The news agency indicated that Morsi has already been interrogated.
MENA said Morsi was being investigated over allegations of collaborating with Hamas "to carry out anti-state acts, attacking police stations and army officers and storming prisons, setting fire to one prison and enabling inmates to flee, including himself, as well as premeditated killing of officers, soldiers and prisoners."
Over recent months, a court in the Suez Canal city of Ismailia has heard testimonies from prison officials and intelligence officers indicating that Morsi and his Brotherhood colleagues were freed when gunmen led by Hamas operatives stormed the Wadi el-Natroun prison. At least 14 members of the security forces were killed and the jail's documents and archives destroyed.
Muslim Brotherhood officials have said they got out when local residents broke into the prison to free their relatives and that they had no knowledge ahead of time of the prison break.
Hamas has consistently denied any involvement. On Friday a spokesman for the militant group, Sami Abu Zuhri, condemned Morsi's detention order.
"The Egyptian decision is an attempt to drag Hamas into the Egyptian conflict," he said. "We call on the Arab League to bear its responsibility in confronting the incitement against Hamas."
Associated Press writers Hamza Hendawi in Cairo and Mohammed Daraghmeh in Gaza City, Gaza Strip contributed to this report.
Copyright 2013 The Associated Press.