According to Khatami, the execution of al-Nimr will remain "a deep wound on the body of the Islamic world," the Iranian Fars news agency reported.
According to the ayatollah, the Organization of Islamic Cooperation (OIC) should respond to the situation. He also reportedly called on Iran’s diplomatic structures to take a decisive stance on the matter.
"I hope that the Islamic world reacts in a way that will make the criminal regime regret its crimes," Khatami, who is also a member of the Assembly of Experts in charge of electing the supreme leader of Iran, said, as quoted by the agency.
Iran's Foreign Ministry spokesman Hossein Jaber Ansari, in response to al-Nimr’s execution, reportedly accused Saudi Arabia of supporting terrorism and executing its opponents.
Earlier in the day, Yemen's Houthi movement mourned al-Nimr as a "holy warrior," describing his execution as a "flagrant violation of human rights," according to media reports.
Lebanon's Supreme Islamic Shiite Council is also said to have condemned the prominent cleric’s execution, saying it was a "grave mistake."
Al-Nimr was arrested by the Saudi authorities in 2012 during protests in the east of the country. In 2014, he was sentenced to death on charges of inciting hatred, disobedience to the king and the establishment of a terrorist cell with the aim to attack law enforcement personnel.
