Egypt's Court of Cassation on Monday upheld 25-year prison sentences against 22 members of the Muslim Brotherhood including the group's Mufti Abdul Rahman Al-Barr, a judicial source said.
The source, who preferred not to be named because he was not authorised to speak to the media, said the court has also supported prison terms ranging from five to 15 years against 290 other defendants.
The verdicts were originally issued by the Cairo Criminal Court in September 2017.
The Court of Cassation's verdict is final and cannot be appealed.
In the wake of these events, the late Attorney General Hisham Barakat referred 491 defendants to the Criminal Court in February 2014.
Prosecutors accused them of committing acts of violence, killing 44 people, assaulting police forces, injuring 59 persons including 22 policemen, and setting fire to public properties.