The United States says it is "deeply concerned" about the death sentences handed down to former President Mohamed Morsi and more than 100 other defendants for a 2011 mass prison break.
"We have consistently spoken out against the practice of mass trials and sentences, which are conducted in a manner that is inconsistent with Egypt's international obligations and the rule of law," a State Department official said Sunday.
The sentences were handed down Saturday in a Cairo court.
The Grand Mufti, Egypt's top religious authority, will make the final decision on the sentences on June 2.
The former president is also facing espionage charges.
A lawyer for Morsi said he would appeal his client's death sentence.
Muslim Brotherhood supporters called for protest against Morsi's death sentence.
The Cairo court also issued a separate verdict against several top Muslim Brotherhood leaders for conspiring with the Hamas and Hezbollah groups in organizing the prison break.
Last month, Morsi - the country's first democratically elected leader - was sentenced to 20 years in prison in connection with the killing of protesters outside the presidential palace in 2012. The criminal court also found 12 other Muslim Brotherhood leaders and supporters guilty of intimidation and violence, but not murder.
The Egyptian military toppled Morsi in 2013 after millions took to the streets accusing his government of abusing its power. Since then, the government of then army chief and current President Abdel-Fattah el-Sissi has jailed tens of thousands of Muslim Brotherhood members and supporters.
6 men hanged for killing soldiers
Egypt has hanged six men convicted of killing soldiers in 2014.
The men, who were hanged Sunday in a Cairo jail, were reported to be members of a Sinai-based militant group with ties to the Islamic State.
The group has been accused of carrying out deadly attacks following the army's overthrow of Islamist President Mohamed Morsi in 2013.
Amnesty International described the men's trial as "grossly unfair."
The rights group had called for a stay of execution, saying that three of the men were already in custody at the time of their alleged crimes.