An estimated 3,000 people protested near the Muslim Brotherhood’s headquarters in the Egyptian capital, clashing with hundreds of supports of the Islamist group.
Riot police fired tear gas to break up the rival groups.
Authorities say around 40 people were injured. Local media reported that Khaled Ali, a liberal politician and a former presidential candidate, is among the wounded.
Opponents of the Muslim Brotherhood believe that the Egyptian government is being unduly influenced by the group. The country’s President Mohamed Mursi is a leading Brotherhood member.
There have been a series of clashes in Egypt in recent weeks, hindering Mursi’s government as it struggles to maintain order and revive the country’s flailing economy.