CAIRO (AFP) - Egypt's Muslim Brotherhood called for an "uprising" on Monday after dozens of supporters were killed outside an elite army headquarters in Cairo, and urged international intervention to prevent a "new Syria."

The Islamist group's political arm, the Freedom and Justice Party, called for "an uprising by the great people of Egypt against those trying to steal their revolution with tanks."

It urged "the international community and international groups and all the free people of the world to intervene to stop further massacres ... and prevent a new Syria in the Arab world."

The call came after at least 34 people were in an attack outside the headquarters of the Republican Guard in Cairo.

Egyptian Health Ministry official Khaled el-Khatib said Monday that initial reports indicated 34 people were killed and 300 wounded in shooting outside the building.

As an immediate consequence, the ultra-conservative Islamist Nour party, which initially supported the military intervention, said it was withdrawing from stalled negotiations to form an interim government for the transition to fresh elections.

Al Jazeera's Egypt news channel broadcast footage of what appeared to be five men killed in the violence, and medics applying cardiopulmonary resuscitation to an unconscious man at a makeshift clinic at a nearby pro-Mursi sit-in.

A Reuters television producer at the scene saw first aid helpers attempting mouth-to-mouth resuscitation on a dying man.

Wounded people were being ferried to the field hospital on motorbikes, given first aid treatment and taken away in ambulances. The military overthrew Mr Mursi on Wednesday after mass nationwide demonstrations led by youth activists demanding his resignation. The Brotherhood denounced the intervention as a coup and vowed peaceful resistance.