Scuffles erupted in Cairo during a protest on October 12 against a court ruling that acquitted Hosni Mubarak-era officials of ordering a camel charge against demonstrators.
The court on October 10 said it didn't find sufficient evidence to convict the defendants in the case, including former parliament speaker Fathi Sorour.
While protesters were united in outrage at the court ruling, supporters and opponents of Islamist President Muhammad Morsi threw stones and bottles at each other.
Medics said at least 40 people were injured in the scuffles, as thousands of people gathered in Cairo's Tahrir Square, the site of some of the biggest protests to oust Mubarak in early 2011.
Egypt does not have a new constitution or parliament yet. Islamists and liberals have been at loggerheads over the constitution, still in the drafting stage.
Based on live television broadcasts and reporting by Reuters and dpa