Intense clashes took place on Friday between hundreds of Muslim Brotherhood supporters and opponents near the group's Cairo headquarters.
At least 40 people have been injured, according to a health ministry source as the number is expected to soar. No deaths were reported.
Police repeatedly fired teargas from the headquarters at anti-Brotherhood protesters throughout the day.
Earlier, protesters had already started gathering for 'Friday of Restoring Dignity' demonstrations at the headquarters in the hilly Cairo suburb to demonstrate against the Islamist group.
Brotherhood members and supporters, in return, formed human chains around the building to protect it from any possible attacks.
The call to protest was prompted after Muslim Brotherhood members and guards reportedly attacked a group of anti-Brotherhood protesters and graffiti artists outside the Islamist group's headquarters on Saturday.
Clashes started at Friday noon in Nafura Square, less than a kilometre away from the headquarters, and continued throughout the day into the evening.
Many protesters suffered head injuries, with the injured being carried to ambulances stationed nearby, said Ahram Online's reporter on the ground.
Former presidential candidate Khaled Ali was injured during the clashes and taken to hospital for treatment.
Meanwhile, buses transporting Brotherhood supporters to Mokattam were torched by protesters.
Demonstrators also attacked and smashed microbuses transporting Muslim Brotherhood members on the main road that leads to the headquarters, as some anti-Brotherhood protesters set up check points.
Gunshots sounds was occasionally heard at the scene, although it was unclear which side the shots were coming from or the type of firearm being used. An Ahram Online reporter saw protesters on both sides carrying firearms.
Mokattam residents, for their side, formed ad hoc neighbourhood watch committees to secure their areas in case clashes reach their homes.
Some residents encouraged anti-Brotherhood protesters from nearby buildings, chanting against the Islamist group from their balconies.
In a statement on Thursday, the interior ministry had called on political currents planning to take part in the protests to avoid getting involved in violence, vowing to be unbiased in its treatment of different political sides.
The ministry stressed its responsibility to ensure citizens' security and to protect public property.
The groups that have responded to the call for protest include the Free Egyptians Party, the Egyptian Social Democratic Party and the Constitution Party, all three coming under the National Salvation Front opposition group.
Hundreds of 6 April Youth Movement members also protested at the New Cairo home of President Mohamed Morsi, who hails from the Brotherhood's political arm, the Freedom and Justice Party.
On their internet media outlet, the group stated its objection to the "rule of the Supreme Guide," accusing Morsi of taking orders from the head of the Muslim Brotherhood and slating the group for its failure in governing the country.
Widespread anti-government sentiment has been evident at recurrent protests across Egypt throughout the past few months.
Other Brotherhood offices were attacked in the cities of Alexandria, Mansoura, Mahalla, and Zagazig.