Updated

Tens of thousands of Mohamed Morsi's loyalists rallied in Cairo Friday, praying for the return of Egypt's first elected president whose whereabouts remained secret more than a week after the military ousted him.

Morsi's Muslim Brotherhood had called the rally in Rabaa al-Adawiya, a square in northern Cairo, where supporters have staged a defiant sit-in since his July 3 overthrow in a popularly backed coup.

With the onset of the Muslim holy month of Ramadan, the Islamist's supporters have turned to prayers as well as numbers in the hope of reinstating the former president.

"God is enough for us, and he is our best custodian," the protesters chanted.

"We are here to deliver a message to the military that we won't give up legitimacy," said Ashraf Fangari, referring to Morsi's election victory in June 2012.

"We will fight for our rights," said the government employee.

Just last month, the Islamists were officially in charge of the country, after decades of persecution led to the 2011 uprising against Hosni Mubarak and Morsi's subsequent election.

But they now find themselves isolated and loathed by the millions of Egyptians who rallied to demand Morsi's ouster -- before the military complied with a swift coup.

In Cairo's Tahrir Square and outside the presidential palace, thousands of Morsi's opponents also gathered on Friday after calls for rival rallies.

Morsi's divisive 12 months in power, after winning the election with an unimpressive margin, and his ouster have polarised the country to levels unseen in years.

"I'll leave as a dead body," said Mohamed Yousry, a teenager at the rally.

"We will defend Morsi with our blood."

Dozens of people were killed in the days leading up to and after Morsi's overthrow.

In the deadliest violence, at least 53 people, mostly Morsi supporters, were killed on Monday in clashes outside an army building where they believed Morsi is being held.

"The military will respond to our demands," firebrand preacher Safwat al-Hegazi told the protesters on Friday.

"We won't leave here until our president, Mohamed Morsi, comes back," added Hegazi, who is wanted by police for questioning on the suspicion that he has incited violence.

With much of the public solidly against him, Morsi has little chance of returning to the presidential palace.

His current whereabouts are a mystery after his detention by the military following his ouster, as is his legal fate.

Authorities have suggested he might face trial on several charges, including insulting the judiciary which was largely hostile to him.

But in Rabaa al-Adawiya, his supporters still have faith.

"I am sure Morsi will return to his position. All injustice comes to an end," said Ibrahim Mohamed, a student from the Nile Delta who came to Cairo for the rally.