CAIRO- Egypt's Court of Cassation upheld a five-year jail sentence against prominent opposition activist Alaa Abdel Fattah on Wednesday, judicial sources said, a final ruling that cannot be appealed.

Abdel Fattah, who has already served more than three years in prison, was jailed for protesting without permission in breach of a 2013 law that rights groups say effectively bans protests.

The blogger and software engineer was a leading voice amongst the tech-savvy liberal youth who initially led the 2011 uprising that ended the 30-year-rule of Hosni Mubarak.

He is one of several activists jailed since the military overthrew Islamist president Mohamed Mursi in 2013 after mass protests and cracked down on his Muslim Brotherhood movement and secular democracy activists.

The government has proscribed the Muslim Brotherhood as a terrorist organisation but denies it has cracked down on secular democracy activists.

Prosecutors said Abdel Fattah was guilty of organising a protest in November 2013 because he had promoted it on social media.

Rights groups say authorities were only able to prosecute Abdel Fattah, who did not attend the protest, by invoking a century old law of assembly that institutes collective punishment for all those involved in an illegal gathering.

They say the 1914-era law was in fact repealed in 1928 and courts should not be using it. They have sued the president over its use but there has been no response from the government.

Abdel Fattah is also on trial in a separate case where he is accused of insulting the judiciary, a charge that carries up to three years in jail. A verdict is scheduled for December.

Egyptian rights activists say they face the worst crackdown in history under general-turned-president Abdel Fattah al-Sisi, who they accuse of erasing freedoms won in the 2011 uprising.

Sisi, seen in the West as a bulwark against extremism in the region, has urged his critics to not judge Egypt's rights records by western standards, saying security and economic prosperity are also human rights.

(Reporting by Haitham Ahmed; Writing by Ahmed Aboulenein; Editing by Jon Boyle) ((ahmed.aboulenein@thomsonreuters.com; +20 2 2394 8097; Reuters Messaging: ahmed.aboulenein.thomsonreuters.com@reuters.net))