Ahmad Maher, a symbol of the popular uprising that ousted autocrat Hosni Mubarak in 2011, turned himself in to the authorities on Saturday after an order was issued for his arrest for defying a new law restricting demonstrations.
The protest law, passed a week ago by the army-backed interim government, has provoked an outcry among rights groups. The army deposed elected Islamist president Mohamed Mursi on July 3, following mass protests against his rule, and the country has seen widespread unrest since.
Maher and around 100 supporters made their way to the Abdeen court, chanting: "Down, down with military rule! I'll write on the prison wall that army rule is shameful and a betrayal!"
Clashes broke out between security forces and activists outside the court after Maher turned himself in. Police fired tear gas and used their batons to disperse the crowd.
Maher will be detained for at least a day one day while his case is investigated, prosecution sources told Reuters.
On Thursday, police arrested activist Alaa Abdel Fattah, also known for his role in the anti-Mubarak uprising. Arrest warrants had been issued for both men after they joined demonstrations outside parliament to defy the protest law.
The new law gives the Interior Ministry the right to ban any meeting of more than 10 people in a public place.
Liberals and activists who backed Mursi's overthrow are becoming more vocal against the military, which has pursued a crackdown against Islamists in which hundreds have been killed and more than 2,000 arrested.
Security forces accuse Mursi's Muslim Brotherhood and their supporters of promoting terrorism and violence. Many of the group's leaders including Mursi have been put on trial.
The group says it rejects violence and accuses the army of staging a military coup against a democratically elected government.