Cairo: Supporters and opponents of Egypt’s ruling Muslim Brotherhood clashed on Friday near the Islamist group’s headquarters on the outskirts of Cairo.

Both sides hurled stones at each other after hundreds of the Brotherhood’s opponents gathered near the headquarters of the group’s Supreme Guidance in the suburban area of Moqattam.

Security forces separated the two sides amid fears about the possibility of renewed violence.

The Brotherhood’s opponents marched to the site in response to a call from the opposition, which accuses the group of oppression and monopolizing power.

“I am not an infidel or an atheist. Down with the rule of the Supreme Guide,” they chanted, referring to the Brotherhood’s spiritual leader.

Meanwhile, angry demonstrators destroyed the office of the Brotherhood’s Freedom and Justice Party in the Cairo quarter of Minyal. There were no reports of casualties. The incident is the latest in a series of attacks on offices of the Brotherhood from which President Mohammad Mursi hails. The group, banned for decades, turned 85 on Friday.

The protests were staged to denounce what the opposition said were attacks by Brotherhood supporters on activists who were spray-painting graffiti critical of the group’s policy near the headquarters at the weekend.

Video clips went this week viral on the internet showing what opposition activists said were Brotherhood supporters wielding batons and knives against opponents. In a clip, a well-built man, allegedly belonging to the Brotherhood, was seen slapping a female activist in the face. Some reporters and cameramen said they had been assaulted too. A senior official in the Brotherhood said Thursday the group would launch an investigation into the incdent and would punish any offender among its members.

The opposition accuses Mursi, who is Egypt’s first democratically elected president, of acting at the group’s command.