Iranian media announced during the weekend that former Vice President Mohammad Ali Abtahi, who served under Reformist President Mohammad Khatami from 1997 to 2001, was found guilty of conspiring against the Islamic republic.
Authorities charged Abtahi with "gathering and plotting against the country's security," issuing propaganda against the cleric regime and insulting Iranian President Mahmoud Ahmadinejad.
Court officials used evidence taken from his personal Web site and interviews with the BBC to back up their claims, London's Daily Telegraph reports.
"Abtahi was sentenced to six years in prison for acting against national security and propaganda activity," authorities said.
The former vice president was arrested in the wake of the post-election unrest that greeted the disputed victory for Ahmadinejad in June elections.
State media showed an Aug. 1 statement from Abtahi saying he encouraged riots during the post-election protests.
Iran has cracked down hard on dissidents in the aftermath the June elections, sentencing five opposition supporters to death last week. Mir Hossein Mousavi, an opposition leader and former prime minister, said his movement, however, would not be deterred.
"This movement will continue and we are ready to pay any price," he said.