CAIRO — Egypt's ruling Muslim Brotherhood said on Monday that armed men who ransacked its national headquarters had crossed a red line of violence, and the movement was considering action to defend itself.

Gehad El-Haddad, spokesman of the Islamist movement, told Reuters in a telephone interview that Egyptians would not sit by and tolerate attacks on their institutions.

"It's very dangerous for one entity in society to take up violence as a means of change because it may entice others to do so. The Muslim Brotherhood is a disciplined organization," he said, criticizing the security forces for failing to protect the headquarters in Sunday's attack.

Haddad referred to the creation of people's self-defense committees during the 2011 uprising that overthrew former President Hosni Mubarak.

Asked whether the Brotherhood was calling for a similar move now, he said the movement's Guidance Bureau was in session and would make an announcement at a news conference later on Monday.

"The people will not sit silent," the spokesman said.