The family of Egypt’s ousted president lashed out at the military Monday, accusing the generals of kidnapping Mohammed Morsi, who has been detained incommunicado in an unknown location for nearly three weeks.

New violence erupted around protests by Morsi supporters demanding his reinstatement, killing at least four people. Pro-Morsi protesters marched near Cairo’s Tahrir Square, battled with Morsi opponents camped out in the square, trading stones and gunfire, while further clashes erupted in a city north of Cairo.

The statement by Morsi’s family at a Cairo press conference underlined the unknown fate of Egypt’s first freely elected president. Morsi has not been seen and has had no known contact with lawyers, family or supporters since the military ousted him July 3 after mass protests nationwide demanding his removal.

Since his ouster, the Islamist leader has become a tool for both sides. The new military-backed government has used Morsi to put pressure on his Muslim Brotherhood, launching criminal investigations without actually bringing charges against him. Government officials have said only that he is safe, is well cared for and is being held for his own protection.

The Brotherhood, in turn, has sought to drum up sympathy by saying Morsi’s detention shows the military’s coup is taking the country into dictatorship, as it tries to expand street protests demanding he be reinstated as president.

European Union foreign ministers Monday called for the release of Morsi and “all political detainees,” saying it was among their key priorities for Egypt’s new leadership. The United States has also urged Morsi’s release. Along with Morsi, at least five other senior Brotherhood figures are in detention.

At Monday’s press conference, Morsi’s daughter Shaimaa read out a statement by the family, saying, “We hold the leaders of the bloody military coup fully responsible for the safety and security of the president.”

One of Morsi’s sons, Osama, described his father’s detention as the “embodiment of the abduction of popular will and a whole nation,” and said the family will “take all legal actions” to end his detention.

“What happened is a crime of kidnapping,” said Osama, who is a lawyer. “I can’t find any legal means to have access to him.”

He said that the family met with Morsi for the last time July 3, shortly before military chief Abdel-Fattah el-Sissi announced the president’s ouster. Since then, they have had no contact with him.

Egypt’s prosecutors have said they are investigating allegations that Morsi and Brotherhood officials conspired with the Palestinian militant group Hamas to carry out a 2011 attack on prisons that broke Morsi and other Brotherhood leaders out of jail during the 18-day uprising against autocrat Hosni Mubarak. However, prosecutors have not formally ordered Morsi detained for investigation — meaning his detention effectively remains outside the legal system.

However, also there also seemed to be a media campaign aimed at further depicting Morsi as turning to outside powers. On Monday, the state-run Al-Ahram daily splashed on its front page claims of a new investigation against Morsi, though the prosecutors’ office and the military quickly denied its report.

On Monday, a senior Brotherhood figure escalated the group’s campaign against the United States, calling on protesters to “besiege” the embassy and expel the ambassador.

Several hundred Islamists tried to march toward the U.S. Embassy, passing near Tahrir Square, where Morsi opponents have been camped out. Rock-throwing clashes erupted between the two sides, and gunshots were heard, though it was not clear who opened fire. Both sides were seen to have what appeared to be homemade pistols.