Mansoor Osanloo, who runs a union grouping bus drivers, was detained in July for “distributing statements against the system”.
Western rights groups say Iran has launched a crackdown on dissenting voices, although Tehran denies this.
“This verdict is certain and he is currently serving his jail sentence,” Hassan Haddad, deputy prosecutor in Tehran, was quoted as saying by the official IRNA news agency, without giving details of the charges.
Iran’s judiciary says Osanloo’s union is an illegal organization. Osanloo has been in jail before.
Haddad was quoted as saying about the case in August: “I told Osanloo ‘your behavior creates problems for the country’s security’ … Because he has traveled abroad he thinks he can do whatever he wants.”
Rights groups and Western governments say Iran this year has launched a fresh crackdown on dissent in the Islamic Republic, with the authorities targeting women’s rights activists, students, journalists and labor figures.
It coincides with an escalating standoff between Iran and Western powers over Tehran’s disputed nuclear program which it says is aimed at generating electricity but which the United States suspects is for building bombs.
The European Union last week said it was “deeply concerned at the growing repression against all groups which exercise their right to freely express their opinions … in the Islamic Republic.”
Iran rejects accusations it is violating human rights and the government of President Mahmoud Ahmadinejad says it supports free speech and welcomes constructive opposition.
The president came to power in 2005 pledging to share out Iran’s oil riches more fairly. But critics say his spending policies have fuelled double-digit inflation and his fiery speeches provoked the United Nations to introduce sanctions.
