Egypt's outlawed Muslim Brotherhood has slammed Tuesday's confirmed death sentences against some of its leading figures, including deposed president Mohamed Morsi, calling on Egyptians to join an “uprising” on Friday.

In a statement on its official Facebook page, after a Cairo court upheld death sentences against Morsi and 99 others in the Wadi Natroun jailbreak case on Tuesday morning, the Muslim Brotherhood described the trial as a "sham", and critisised the judges for describing it as being “for the 25 January revolution" that toppled long-time autocrat Hosni Mubarak in 2011.

The Muslim Brotherhood called on Egyptians to protest the verdicts on Friday, in what they described as “a popular uprising”.

Just hours before the trial, in an email to foreign correspondents in Egypt, the Muslim Brotherhood's press office in London had stressed that a "peaceful approach" was the best strategy in the "revolution against the coup", referring to the group's opposition to Egypt's current regime, whom they accuse of having conducted a military coup to oust democratically-elected Islamist president Morsi from power in July 2013.

On Tuesday, the Cairo court also sentenced Morsi to life in jail and 16 others to death on charges of "conspiring with foreign powers", including Palestinian group Hamas and Lebanese movement Hizbollah.

Sondos Essam, a former Brotherhood spokesperson and the only woman sentenced to death in the case, slammed the verdicts on her Facebook page.

“The Egyptian judicial system has become completely politicised," wrote Essam, who was sentenced in absentia and is currently in the UK. "The many hundreds currently sentenced to death have not been afforded the basic protection of their right to a fair trial and due process before an independent judiciary.”

Earlier on Tuesday, Turkey’s President Tayyip Erdogan described the death sentence issued for Morsi as a “massacre of law”.

"We call on the international community to act to withdraw these death sentences, given under the instructions of the coup regime, and to put an end to this path which could seriously endanger the peace of Egyptian society," he said in a statement.

United Nations Secretary-General Ban Ki-moon is "deeply concerned" that deposed Egyptian President Mohamed Morsi and more than 90 other people were sentenced to death on Tuesday over a mass jail break during the country's 2011 uprising.

"The United Nations is against the use of the death penalty in all circumstances," Ban's press office said in a statement. "The Secretary-General is concerned that such verdicts, handed down after mass trials, may well have a negative impact on the prospects for long-term stability in Egypt."

The White Househas also branded Egypt's sentencing of former Morsi as politically motivated Tuesday, in a sharp rebuke of its uneasy military ally.