Egypt's ruling Muslim Brotherhood warned on Thursday that it will defend its headquarters as hundreds of its members gathered outside the building ahead of an opposition protest.
The Islamists were bussed in to stand guard outside the building in Cairo, where opposition activists who plan to hold a protest on Friday had previously clashed with Brotherhood members.
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.
Primarily, "the protection of private and public property is the responsibility of the police," the group's secretary general Mahmud Hussein told a news conference.
"But the owner of every house has the right to defend it using all means. If the police don't carry out their responsibility, we will protect our property with all we posses," he added.
Activists, including often violent Black Bloc protesters, have called for a demonstration outside the Brotherhood's Cairo headquarters on Friday, almost a week after they clashed with the Islamists and police guarding the building.
Hussein cut short the chaotic news conference after angry journalists kept drowning him out. Some reporters said they and colleagues had been assaulted by Islamists during the clashes last Saturday.
The confrontation marked a new low in relations between the increasingly secretive Islamic group and a hostile domestic media, which has complained of censorship under Egypt's new Islamist leaders.
The Brotherhood, well organised despite decades of persecution by overthrown president Hosni Mubarak and his predecessors, was the winner of parliamentary and senate elections last year.
But its critics accuse it and Morsi of mirroring the tactics used by Mubarak, overthrown in 2011, against the opposition.