CAIRO:Fifty-one loyalists of Egypt's ousted president were killed Monday while demonstrating against last week's military coup, triggering an Islamist uprising call and dashing the army's hopes for an interim civilian administration.

The Muslim Brotherhood, which has led demonstrations against Wednesday's overthrow of Islamist president Mohamed Morsi, said its supporters were “massacred” by troops and police during dawn prayers in Cairo.

Witnesses, including Brotherhood supporters at the scene, said the army fired only tear gas and warning shots and that “thugs” in civilian clothes had carried out the deadly shooting.

The Muslim Brotherhood'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.”

Morsi loyalists seize two Egypt soldiers: army

Meanwhile, armed supporters of the ousted president seized two soldiers in Cairo after the earlier clashes, an army official said.

Both of the Egyptian soldiers, who were identified as Samir Abdallah Ali and Azzam Hazem Ali, “managed to escape their captors”, the official said.

The two had been put in a vehicle and forced to make pro-Morsi and anti-army statements on a loudspeaker, said the official, cited by state news agency MENA. One soldier had been “severely beaten up” and filmed while making the pro-Morsi statements, he added.

ElBaradei condemns killings, urges independent probe

Prominent Egyptian liberal leader Mohamed ElBaradei condemned the killing of at least 42 people outside the army headquarters and called for an independent investigation.

“Violence begets violence and should be strongly condemned. Independent Investigation a must. Peaceful transition is only way,” the Nobel Peace laureate said on his official Twitter account.

The National Salvation Front, a coalition of liberal and leftist groups headed by ElBaradei, also called for a transparent investigation into the events.

The NSF “strongly condemns” the violence and called for “an urgent and fair investigation into the tragic events that took place at dawn in front of the Republican Guard headquarters, and that the results be published transparently to the public.”