Egypt's Muslim Brotherhood has called on supporters of the country's ousted president Mohamed Morsi to take part in a further protests tomorrow.

The call to "rise up" against the military came after at least 51 people were killed and more than 400 injured in clashes on Monday.

The army claims it opened fire because "a terrorist group" tried to storm an army compound, where former President Mohamed Morsi is believed to be held.

But Morsi supporters said they were shot in a "massacre" during morning prayers.

ITV News' International Correspondent John Irvine reports.

Hatem Azam, a spokesman for a coalition led by the Muslim Brotherhood, said:

"In protest against the military coup that was followed by suppressive actions, topped by the Republican Guard massacre that took place at dawn, we call on all citizens and honourable people to protest on Tuesday across Egypt".

The United States remains concerned about the increasing violence and political polarisation in Egypt, White House spokesman Jay Carney said.

The US State Department has called on the Egyptian army to exercise "maximum restraint" in dealing with protesters.

The White House has expressed concerns about the escalating unrest.

Washington also said it is reviewing whether the military's action in Egypt to depose President Mohamed Morsi was a coup.

The US currently provides financial support to Egypt, particularly its military and would be faced with a predicament if the status of Morsi's removal was considered as such.

However, the White House added that cutting aid to Egypt now is "not in the best interests of the United States".

General Abdel Fattah al-Sisi announced President Morsi's removal from office last week.

Earlier, Egypt's Nour Party announced its "withdrawal from all tracks of negotiations as a first response" to the shootings.

The country's interim leader Adly Mansour has expressed his sorrow and ordered an investigation into the deaths.