Tens of thousands of supporters of ousted Egyptian president Mohamed Morsi massed Friday to demand his reinstatement, signaling that they will not surrender their challenge to the new government installed by the country’s powerful military.

The biggest gathering was at the Rabaa al-Adawiya mosque in the Cairo suburb of Nasr City, which has been transformed into a permanent protest camp with tents echoing the ones set up by secularists and liberals in the city’s Tahrir Square. A big banner proclaiming “No to Military Rule” greeted arrivals, who were chanting Morsi’s name and waving his picture.

Morsi’s whereabouts have been unknown since he was detained by the military 10 days ago, and in Washington, the State Department said Friday that it agreed with a call by Germany for the ousted president’s release.

“We do agree,” spokeswoman Jen Psaki said when asked about Germany’s appeal to the Egyptian authorities to release him. It was the first time the U.S. government has publicly suggested that he be set free.

Psaki also said that U.S. Ambassador to Egypt Anne W. Patterson has met Egypt’s interim president, Adly Mansour, who was appointed by the military after Morsi was overthrown.

The Obama administration has strenuously resisted describing as a coup the events of last week, in which Morsi was ejected from office by soldiers who took him into custody at his office, after millions of Egyptians took to the streets to demand that he go. The U.S. response has prompted anger from Muslim Brotherhood supporters who interpret the refusal as a sign of possible U.S. complicity in Morsi’s downfall.

“Obama, you have made a big mistake in not supporting democracy,” fumed one of the protesters, Sidi Atta, who had traveled from the Nile Delta to attend Friday’s gathering.

Overshadowing the event were the deaths Monday of at least 51 protesters who were shot by the army in unclear circumstances at another protest site in Cairo. Photographs of the slain men, some of them teenagers, hung over many of the tents, along with pledges not to let their deaths be in vain.

“With the blood of our martyrs, we will have a second revolution,” chanted a group of men as they arrived at the mosque.

Others chanted “Sissi Sissi Sissi, leave leave leave,” a reference to the army chief, Gen. Abdel Fatah al-Sissi, who was depicted on posters with blood dripping from his mouth.

But the mood was festive, with entire families showing up with baskets of food to break the daily fast they are observing during the holy month of Ramadan. Because many Egyptians are abstaining from food and drink between sunrise and sunset, protests now are being held in the evening, rather than during the day. Families were invited to celebrate the fast-breaking meal of iftar together as a means of expressing their opposition to the military takeover.

“We are not slaves. We are free. We will sacrifice only to God,” shouted one of the preachers on the podium, as people who had not eaten all day milled around in the hot sun, and others dozed on mats and blankets under awnings.

Brotherhood supporters wearing hard hats and carrying sticks guarded the site and said that they were determined to keep the protests peaceful. “If they shoot us, we will bring marchers in their millions,” said Osama Ashraf Arafa, 18, one of the guards, who came from the Nile Delta town of Mansoura.

The crowds drawn to pro-
Morsi demonstrations were far smaller than those that turned out to demand that he leave office. Many of those protesters had voted for Morsi but felt betrayed by the dismal performance of his government in the year it spent in office.

Not all of those who turned out Friday were Muslim Brotherhood supporters.

“I am Egyptian, I am not Brotherhood,” said Hosni Ibrahim, 48, an engineer, who said he had come to express his support for democratic principles. “Our president was betrayed by a military coup, and we have no alternative but to resist.”