The national Muslim Brotherhood headquarters was stormed early on Monday morning, reports Egyptian state news agency, MENA.
Hundreds surrounded the headquarters in the isolated, hilly Cairo district of Moqattam. Some threw rocks and petrol bombs at the building, which caught on fire as guards and Brotherhood members inside the building exchanged gunfire with the attackers. The fire was quickly controlled.
As the Brotherhood members and guards were fleeing, they shot live ammunition at people gathered outside.
One of the Brotherhood members was beaten and is currently in critical condition, according to MENA.
Eight protesters died and at least 38 were injured, the health ministry tells Ahram Online.
In his tweets, senior FJP official Gehad El-Hadad hinted that the assailants may be linked to the banned 'Black Bloc' group; a youth group that wear black masks and often resort to violence during protests.
Several other Brotherhood-affiliated offices were also assaulted.
A number of Brotherhood buildings have come under attack as tensions have mounted in the lead-up to the 30 June demonstrations, with the group's offices in Alexandria and the Nile Delta governorates of Sharqiya, Gharbiya and Beheira being firebombed or ransacked.