In a statement on Saturday, the union expressed deep condolences over the martyrdom of Sheikh Nimr.
It slammed the Al Saud dynasty and emphasized that the “bloodthirsty” Saudi regime, which is on the verge of collapse, is doing whatever it can, including attacking Yemen, killing children, repressing and executing dissidents, just to survive.
In the statement, the union also called on the Iranian people to stage rallies in front of the Saudi Arabian embassy in Tehran to condemn the execution of the Shiite leader.
Saudi Arabia executed 47 prisoners on Saturday, including Sheikh Nimr, the Arab country’s interior ministry said in a statement.
The cleric’s name was among a list of the 47 carried by the state-run Saudi Press Agency. It cited the interior ministry for the information. Saudi state television also reported the executions.
Sheikh Nimr was detained in July 2012 on charges of delivering anti-regime speeches and defending political prisoners.
His arrest sparked widespread protests in the Arab country, leaving several people dead.
In 2014, a Saudi judge found him guilty of “sedition” and sentenced him to death.
In October 2015, a Saudi appeals court upheld the death sentence, referring his case to King Salman’s office.
United Nations Secretary General Ban Ki-Moon, among many others, had called on Riyadh to halt the execution of Sheikh Nimr.