At least 40 people have been killed in clashes outside a military building in Cairo where supporters of the former president were holding a sit-in.

Following a day of massive rallies against the ousted Egyptian President and an early morning shooting of pro Mohamed Morsi supporters outside a Presidential Guard barracks, members of the Egyptian military and their supporters guard a bridge near Tahrir Square ( Spencer Platt/Getty Images)

An Egyptian health ministry official says initial reports also indicate at least 322 were wounded.

Military spokesmen said gunmen opened fire on troops at the building, killing at least five supporters of Mohammed Morsi and one officer.

But a spokesman from Morsi's Muslim Brotherhood and a witness at the scene say military forces opened fire at dawn today on the protesters outside the Republican Guard building. The different accounts could not be reconciled.

Satellite broadcaster Al-Jazeera showed footage from a nearby field hospital of at least six dead bodies laid out on the ground.

A medic from the area says ambulances were unable to transport more than 200 wounded to hospitals because the military had blocked off the roads.

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