Egyptian Muslim Brotherhood members gathered behind police lines outside their Cairo headquarters on Friday in anticipation of an opposition march, a week after activists clashed with the Islamists.
The Brotherhood bussed in hundreds of supporters to stand guard outside its offices ahead of the opposition protest, set to begin after noon on Friday.
Police deployed around the building in Mokattam, a middle class Cairo neighbourhood where the once-banned Brotherhood built its headquarters after a 2011 uprising overthrew its foe president Hosni Mubarak.
A senior Brotherhood member said on Thursday the Islamists would defend their headquarters if police failed to protect it.
The Brotherhood has seen about 30 of its offices across the country attacked in widespread protests against President Mohamed Morsi, the Islamists' successful candidate in last June's election.
Activists, including often violent Black Bloc protesters, had called for a demonstration outside the Brotherhood headquarters on Friday, almost a week after they clashed with the Islamists and police guarding the building.
The Brotherhood, well-organised despite decades of persecution under Mubarak and his predecessors, was the main winner of parliamentary and senate elections last year.
But its critics accuse it and Morsi of mirroring the tactics used by Mubarak against the opposition.