Tens of thousands of protesters are on the streets of Egyptian cities in rival shows of force by supporters and opponents of Mohamed Morsi, ousted as president by the military last week.
Mohamed Morsi’s supporters have gathered outside a mosque and a barracks in Cairo to demand his reinstatement.
Anti-Morsi protesters are rallying in the capital’s Tahrir Square.
Mohamed Morsi, Egypt’s first Islamist president, is in detention, along with some senior Muslim Brotherhood figures.
He was replaced on Thursday by Adly Mansour – the head of the Supreme Constitutional Court – who promised to hold elections soon but gave no date.
The military has deployed troops in Cairo and other locations. More than 30 people were killed and about 1,000 people injured across Egypt in protests on Friday.
Mohamed Morsi’s supporters have been camped outside the Rabaa al-Adawiya mosque in Cairo for more than a week. On Sunday, thousands marched from the mosque to the barracks of the Presidential Guard, where they believe Mohamed Morsi is being held.
Another group of pro-Morsi marchers are heading for the ministry of defense.
Tamarod, the opposition movement whose name means “rebel” in Arabic, called on its supporters to rally in Tahrir Square and at the Ittihadiya presidential palace.
Egypt military planes flew overhead, trailing plumes of smoke in red, white and black, the colors of the national flag.
There is still no word on whether pro-reform leader Mohamed Elbaradei has been appointed as interim prime minister.
Tamarod has tweeted that it will not accept anyone except Mohamed ElBaradei, a Nobel laureate and former head of the UN nuclear agency, as prime minister.
However, the ultra-conservative Salafist al-Nour party is said to be unhappy with Mohamed ElBaradei, whom its members view as too secular.
In other developments, plain-clothes police raided the main office of al-Jazeera’s Arabic TV channel in Cairo on Sunday and arrested the bureau chief.
Abdel Fattah Fayed is accused of operating an unlicensed channel and broadcasting reports that had a negative impact on national security.
Meanwhile, 11 activists have been acquitted of inciting violence and destroying public property, the Egyptian state news agency Mena reported.
The group – which included the blogger Ahmed Douma – was facing charges relating to clashes with Muslim Brotherhood supporters outside the organization’s headquarters in March.
Tamarod – which organized the recent anti-Morsi protests – had accused the ousted president of pursuing an Islamist agenda against the wishes of most Egyptians, and of failing to tackle economic problems.
The US and other Western countries have expressed concern over Mohamed Morsi’s removal, and have called for reconciliation and speedy elections.