Prosecutors have opened an investigation of ousted Egyptian President Mohammed Morsi on charges including murder and conspiracy with the Palestinian militant group Hamas, fuelling tensions amid a showdown in the streets between tens of thousands of backers of the military and supporters calling for the Islamist leader's reinstatement.
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 neighbourhood and in the Nile Delta city of Damietta with at least 18 injured, according to health officials.
The announcement of the case against Mr 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 mR Morsi denied the charges against him, calling them politically motivated but vowed to keep their protests peaceful.
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 then president Hosni Mubarak in which gunmen attacked a prison north-west of Cairo, freeing prisoners including Mr Morsi and around 30 other figures from his Muslim Brotherhood. The prosecutors allege Mr Morsi and the Brotherhood worked with Hamas to carry out the break, in which 14 guards were killed.
US State Department spokeswoman Jen Psaki expressed deep concern about reports of Mr 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."