Amnesty International urged Iran on Saturday not to execute a political dissident convicted of "enmity against God" in what it said had been an unfair trial, as his family said they feared he would be hanged within hours.
Gholamreza Khosravi Savajani was sentenced in 2010 in connection to alleged links with the People's Mujahideen Organisation of Iran (PMOI) a group that seeks to overthrow the Islamic Republic, Amnesty says.
The PMOI, which has an office in Paris, said Savajani's family had been summoned to the jail where he was being held and had been told he would be executed on Sunday morning.
"Yet again Iranian authorities are about to execute a man who did not even receive a fair trial in total disregard of both international law and the Iranian law," said Hassiba Hadj Saharoui, of London-based Amnesty International.
Iran says its judicial system is fair and accuses Western powers of using accusations of human rights abuses as a way to undermine it.
Human rights groups say Iran executes more people as a proportion of the population than any other country and U.N. Secretary-General Ban Ki-moon said in March that the rate of executions had risen since the election of President Hassan Rouhani last year.
In the last execution in Iran that received international attention, Iranian media reported last week the hanging of the first of four men sentenced to death for a financial scam that tainted the government of former President Mahmoud Ahmadinejad.