(CNN)Iranian conservative cleric Ayatollah Mohammad-Taqi Mesbah Yazdi died in Tehran on Friday, according to Iran's state-run Islamic Republic News Agency (IRNA).
The Imam Khomeini Educational and Research Institute, which Mesbah Yazdi headed, said he had been hospitalized over the past few days with a disease to his digestive system.
The prominent cleric played a major part in the 1979 uprising that overthrew the Western-backed Shah of Iran, Mohammed Reza Pahlavi, according to Iran's state-run Press TV.
Mesbah Yazdi was seen as a hardliner and anti-West in general, including holding anti-US positions. An outspoken critic of a liberal press, he was known to have ratified crackdowns on domestic opposition, feminism and gender equality.
According to regional experts, he was a spiritual mentor to Mahmoud Ahmadinejad, the former Iranian President who served from 2005 to 2013.
Iranian President Hassan Rouhani offered condolences on Mesbah Yazdi's passing, according to Press TV, which reported Mesbah Yazdi was 85 years old.
Iran's semi-official Mehr news agency said Mesbah Yazdi was close to the country's Supreme Leader Ayatollah Ali Khamenei.
Mesbah Yazdi was a member of the Assembly of Experts — the body responsible for electing and monitoring the performance of Iran's Supreme Leader — and the Supreme Council of Cultural Revolution, Press TV reported.