Iran supreme court upholds death sentence for opposition figure
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The Islamic Revolutionary Guard Corps announced the arrest of Zam in October last year, calling him a "counter-revolutionary" who was "directed by France's intelligence service".
He was charged with "corruption on earth" -- one of the most serious offences under Iranian law -- and sentenced to death in June.
It "upheld the ruling issued by the Revolutionary Court," he added, speaking at a videoconference.
Zam, who reportedly lived in Paris, ran a channel on the Telegram messaging application Amadnews.
At the time, he was accused by authorities of playing an active role in anti-government protests sparked by economic hardship between December 28, 2017 and January 3, 2018.
At least 25 people were killed during the unrest.
Telegram shut down Amadnews after Iran demanded it remove the account for inciting an "armed uprising".
According to Zam's indictment published in February, he was accused of having "committed offences against the country's internal and external security" and "espionage for the French intelligence service", alongside "corruption on earth".
He was also accused of having insulted the "sanctity of Islam".