Updated

Egypt's Muslim Brotherhood on Thursday sharply criticized the military for ousting the country's Islamist president, comparing its rule to that of Adolf Hitler or Roman emperor Nero -- remarks likely to stoke tensions ahead of rival rallies by supporters and opponents of the former leader.

The criticism was particularly stinging, even by Brotherhood standards. The group has delivered successive anti-military pronouncements in the three months since Mohammed Morsi, Egypt's first freely elected president and one of the group's longtime leaders, was toppled in a popularly-backed military coup.

Since Morsi's July 3 ouster, the country's military-backed government has moved against the Brotherhood, banning the group, seizing its assets and arresting hundreds of its supporters.

The rival rallies on Sunday -- both planned in Cairo's central Tahrir Square -- carry the potential for violent clashes between Morsi's Islamist supporters and Egyptians who back the military.

The date is also a national holiday, marking the 40th anniversary of the start of the 1973 Middle East war in which Egyptian forces made initial gains against Israel.

"If history will mention the 1973 (military) commanders on its brightest pages, there is no doubt that it will mention the leaders of the bloody coup who murdered their Egyptian brothers on the same page with Nero, (the Mongol leader) Hulagu and Hitler," the Brotherhood statement said.

The statement also urged Egyptian troops to rebel against their commanders and said it hoped that Sunday will mark a "victory by the people over those who the staged a coup against them for personal gain."

An umbrella of Islamist groups led by the Brotherhood, issued a separate statement with similar calls for soldiers to stage a mutiny against their commanders, saying the military must end its involvement in Egyptian politics and focus on the defense of the country instead. The National Alliance for Supporting Legitimacy urged opponents of the coup to gather at squares across the nation on Friday and in Tahrir Square on Sunday.

Since his ouster, Morsi has been detained by the military in an undisclosed location while the military-backed authorities cracked down on the Brotherhood, rounding up more than 2,000 of its members and activists, including spiritual leader, Mohammed Badie, and his powerful deputy, Khairat el-Shater. Many of those detained are facing charges that range from conspiring with foreign powers and incitement of violence to corruption and murder.

Morsi supporters have in the meantime staged daily protest across much of Egypt, but the numbers taking part in these marches has steadily dwindled in recent weeks.

Also Thursday, EU's foreign policy chief, Catherine Ashton, held talks with officials in Cairo in an effort to defuse Egypt's political crisis. She met interim President Adly Mansour and the military chief, Gen. Abdel-Fattah el-Sissi, in what was her third visit to Egypt in as many months.

The planned protests and fears of renewed violence highlight the turmoil that continues to engulf Egypt and which threaten to derail or delay the military-backed road map announced on the day of Morsi's ouster and which concludes with presidential elections early next year.

Clashes on Wednesday between Morsi's supporters and opponents in the Red Sea city of Suez left a 16-year-old boy dead, according to Reda Zaghloul, emergency chief at the city's main hospital.