Amnesty International has appealed to Iran to commute the death sentence of an Iranian Kurdish student who it says is expected to be executed on Sunday.
Habibollah Latifi, 29, has been found "guilty of waging war against God" by co-operating with a banned Kurdish rebel group - a charge he denies.
The human rights group says his trial was held behind closed doors with no legal representation and was unfair.
It says Tehran should now "show clemency" and halt the execution.
Between 20 and 30 people protested on Saturday night outside the Iranian embassy in Paris against the impending execution. Several chained themselves to railings.
"While we recognise that governments have a responsibility to bring to justice those who commit crimes, this must be done according to international standards for fair trial," said Malcolm Smart, Amnesty International's Middle East and North Africa director.
"It is clear that Habibollah Latifi did not receive a fair trial by international standards, which makes the news of his impending execution all the more abhorrent."
Habibollah Latifi was sentenced to death in 2008 for waging war against God (mohareb) by committing acts of violence as a member of the Party of Free Life of Kurdistan (PJAK) in Iran's western province of Kordestan in 2007.
His death sentence was upheld by an appeals court in 2009.
The law student admitted being a PJAK supporter but denied committing any violence, his lawyer says.
He says that the execution is scheduled at a prison in Sanandaj - the capital of Kordestan - early on Sunday.