Iranian cleric Ayatollah Mohammad Taghi Mesbah-Yazdi, considered the spiritual leader of the most fundamentalist hard-liners, has died in Tehran at the age of 86.

A veteran revolutionary close to Supreme Leader Ayatollah Ali Khamenei, Mesbah-Yazdi died of a gastrointestinal disease after several recent stints in the hospital, Iranian state media reported on January 1.

A fierce opponent of reforms, Mesbah-Yazdi was also known as a supporter of ultraconservative former President Mahmoud Ahmadinejad before having a falling out with him.

To his opponents, the fundamentalist spiritual head of the Paydari Front political faction was one of the most disliked and radical figures.

At the time of his death, Mesbah-Yazdi was the head of the of Imam Khomeini Education and Research Institute and a member of the Assembly of Experts, a clerical body that chooses the supreme leader.

With reporting by AFP, AP, and RFE/RL’s Iran Service.