Police used teargas and birdshot on Sunday evening to disperse roughly 3000 anti-Muslim Brotherhood protesters who had gathered outside the Brotherhood's headquarters in the Cairo district of Moqattam.
Police vehicles also chased down protesters in the streets surrounding the group's headquarters, arresting dozens including journalist Mohamed Rashad.
Activist Dalia Sami, present at the clashes, said in a televised interview with the private OnTV channel that the protest had been peaceful in nature but that security forces had responded with teargas and birdshot.
For his part, Central Security Forces (CSF) General Medhat El-Shafei, in charge of CSF forces in the area, told OnTV on Sunday night that some protesters had fired birdshot at security forces.
"The protest was peaceful at first, but suddenly protesters began hurling rocks [at CSF personnel] so we responded with teargas," El-Shafei said. "Then they began throwing Molotov cocktails and blocking the road with burning tyres and firing [shotguns loaded with] birdshot."
He said that one police officer and two soldiers had sustained injuries as a result.
El-Shafei also confirmed that police had arrested 21 violent protesters during Sunday's clashes.
Limited clashes erupted on Sunday evening after hundreds of protesters headed to the group's headquarters on Sunday afternoon to protest an attack against graffiti artists and activists by Brotherhood members on Saturday. Protesters denounced the attack, especially those on female activists.
A video circulating online showing female activist Mervat Moussa being slapped by a Brotherhood member caused considerable anger among activists and social media users.
Skirmishes subsequently broke out late Saturday night between protesters and security forces outside the group's headquarters.
Shortly after the incident on Saturday night, Brotherhood spokesman Mahmoud Ghozlan stated that protesters, along with some journalists and photographers, had been involved in “provocative” acts outside the group's headquarters.
Protesters chanted against President Mohamed Morsi and the Islamist group from which he hails, holding banners aloft reading "Down with Brotherhood rule."
Clashes broke out after a group of protesters tried to advance on the group's headquarters, which was guarded by security forces.
The latter used teargas to disperse the crowds, while protesters set fire to tyres in the street.
Several anti-Brotherhood Facebook pages have called on members of the public to march from Cairo's Talaat Harb Square to the Brotherhood's headquarters to protest Saturday's attack on the activists.
According to eyewitnesses, a group of Brotherhood members surrounded the building to protect it.