Iranian authorities accused a group of minority Arabs with the 2011 deaths of police officers during a protest. Some were thought to have been convicted of "sowing corruption" and other charges that carry the death penalty in Iran.
Human Rights Watch reported this week that it suspected the men were executed. A trio of U.N. envoys on Iran and summary executions said they were concerned about the executions given the gravity of the crimes and the alleged lack of transparency during court proceedings.
"Under international law, the death penalty is the most extreme form of punishment, which, if it is used at all, should be imposed only for the most serious crimes," they stated.
They described as "cruel" the Iranian practice of carrying out executions in public. Any execution conducted outside of the boundaries of international obligations is considered arbitrary, they added.
Iran is suspected of carrying out at least 140 executions since the beginning of the year. Most were for drug-related offenses.
The experts called on Tehran "to halt immediately the imposition of the death penalty for crimes which do not constitute the most serious crimes, as well as ensure stringent respect for fair trial guarantees."
Notable deaths of 2014 [PHOTOS]