An Egyptian court has confirmed the death sentence given to Mohamed Badie, leader of the now-outlawed Muslim Brotherhood, and 13 other members of the group for "inciting chaos and violence", and has given a life term imprisonment to a US-Egyptian dual citizen for having alleged "ties to the Brotherhood".

The men sentenced on Saturday were among thousands of people detained after Mohamed Morsi, the nation's first democratically-elected president, was overthrown in 2013 by the military under Abdel Fattah el-Sisi, who is now president.

Sisi describes the Brotherhood as a major security threat and has pledged to "eradicate" the group. The group says it is committed to peaceful activism and has nothing to do with violence in Egypt since the coup, which followed large-scale protests against Morsi.

Egypt's mass trials of Brotherhood members and people accused of links to the group, as well as its tough crackdown on Islamist and liberal opposition alike, have drawn international criticism of its judicial system and human rights record.

The sentences, pronounced at a televised court session, can be appealed before Egypt's highest civilian court in a process that could take years to reach a final verdict.

US citizen sentenced to life

US-Egyptian dual citizen Mohamed Soltan, who has been on hunger strike for over one year, was sentenced to life in jail for allegedly supporting the movement and transmitting false news. He is the son of Brotherhood preacher Salah Soltan, who was among those sentenced to death.

Soltan's family called for Mohamed's immediate release in a statement after the verdict, charging that there was no evidence against him. A website calling for his release says he was not a member of the Brotherhood, describing him as a US-educated peace activist who was involved in youth events and charities.

The website shows pictures of him lying emaciated on a stretcher while in detention.

The US embassy, in a statement, said it was "gravely concerned" about Mohamed Soltan and would "continue to monitor his case closely and to provide him with all possible support."

"Rabaa Operations Room"

Mohamed Abdel-Mawgod, one of the defence lawyers, condemned the verdicts. "The court did not differentiate between the defendants and put them all in the same basket," he told reporters at the courthouse. None of the defendants were present during the hearing.

Badie is the Brotherhood's General Guide and has already been sentenced to several death and life sentences. His deputy Khairat El-Shater was given a life sentence on Saturday.

Saturday's case was known in local media as "The Rabaa Operations Room" trial. This is in reference to a sit-in at Rabaa square in 2013 in which hundreds of people protesting the military coup were killed when security forces tried to clear the area by force.

Rights groups say Egypt is now cracking down on all dissent. Sisi says stability is needed to revive the shattered economy.

Rights advocates have criticised a US decision to end a freeze on military aid to Cairo, saying Washington is putting human rights on the backburner. The United States has said the decision to end the freeze was in the interest of national security.