Clash leaves at least 51 dead in Egypt.

By Tom Perry and Alexander Dziadosz

CAIRO, July 8 (Reuters) The death toll rose to 51 on Monday when Islamist protesters, dissatisfied with the ouster of President Mohamed Morsi, said they were shot by soldiers during morning prayers at the Cairo barracks where he is being held.

According to the military's version of events, a "terrorist group" attempted to invade the Republican Guard barracks, leaving one soldier dead and 40 wounded. A military source said the soldiers reacted to the attack.

Emergency services said more than 320 people were injured in a serious escalation of Egypt's political crisis. The Muslim Brotherhood, which supported Morsi, called on its supporters to rebel against the army, which on Wednesday ousted Morsi in a coup with broad popular support.

At a hospital near the Rabaa Addawia mosque, where Islamists have been camped since Morsi's ouster, the rooms were overflowing with people wounded in the clashes. There were blood-stained sheets, and medical teams rushed to attend to the victims.

In response to the violence, the ultraconservative Islamist party Nour, which initially supported the military intervention, decided to abandon the stalled negotiations to form a provisional government to lead the transition until new elections.

The military argues that Morsi's deposition was not a coup d'état, as it fulfilled the desires of millions of Egyptians who took to the streets on June 30 demanding the resignation of Morsi, the first freely elected president in Egyptian history.

Clashes between supporters and opponents of Morsi continue in Cairo, Alexandria, and other cities. At least 35 people died on Friday and Saturday.

The crisis leaves the most populous Arab country, with 84 million people, in a delicate situation, risking greater political polarization and a worsening economic crisis.

Except for the confrontation at the Republican Guard barracks, the atmosphere in the rest of Cairo is relatively calm, but armored vehicles are blocking bridges over the Nile, where there have been serious incidents in recent days.

Negotiations to form the new government were already complicated before Monday's confrontation, as the Nour Party had rejected two liberal candidates for the post of prime minister, presented by interim president Adli Mansour.

The participation of Nour, Egypt's second-largest Islamist party, would be vital for the interim government to have a veneer of Islamist support. The party withdrew from negotiations in protest against what it described as a "massacre in the Republican Guard."

For many Islamic activists, Morsi's ouster was a major setback that sparked fears of a return to the era when the Muslim Brotherhood was harshly repressed by autocratic regimes, including that of Hosni Mubarak, who was overthrown in a popular uprising in 2011 as part of the so-called Arab Spring.

On the other side of the political polarization, millions of Egyptians were happy to see the overthrow of a leader who, in the opinion of liberals, was orchestrating a subtle takeover of the state by Islamic power – something the Brotherhood vehemently denies.

(Additional reporting by Shadia Nasralla, Ashraf Fahim, Asma Alsharif, Mike Collett-White, Alexander Dziadosz, Maggie Fick, Tom Finn, Sarah McFarlane, Tom; Perry, Yasmine Saleh, Paul Taylor and Patrick Werr)