Protesters have stormed and ransacked the Cairo headquarters of President Mohammed Morsi's Muslim Brotherhood Islamist group.

An Associated Press video journalist at the scene says protesters stormed the six-story building in an eastern Cairo district Monday morning, leaving the heavily fortified villa with furniture and files.

Footage on local TV networks showed smashed windows and smoke billowing out of the building. One protester was seen removing the Muslim Brotherhood sign from the building's front wall.

The storming of the Brotherhood's headquarters followed overnight clashes between armed Morsi supporters barricaded inside the building and young protesters pelting it with firebombs and rocks. Activists say at least five protesters were killed in the violence.