|Montazeri's criticism to the Islamic state won him al-Khomeini's wrath
Grand Ayatollah Hossein Montazeri was one of the key leaders of the Iranian Islamic revolution in 1979, which abolished the monarchy and overthrew Mohammad Reza Pahlavi, the Shah of Iran.
The Islamic Iranian Republic was born with Ruhollah al-Khomeini, one of Montazeri’s early religious teachers at the top of the ruling hierarchy.
Montazeri believed that democracy was the best possible way to rule the state, but supported al-Khomeini's controversial concept of Wilayat al-Faqih, which gives the state's religious leader absolute control.
Montazeri was born in 1922 in Najafabad in Iran for a peasant family. He left his home town in his teens to undertake religious studies in Qom, Iran's centre for religious studies. He was tutored by al-Khomeini and was impressed by him.
He soon became active in the clerical struggle to overthrow the Shah. He was imprisoned in 1974 for his political outlook and was sentenced to death.
The death sentence was later waived and Montazeri was released in 1978, just a a few months before the revolution.
In the wake of the Islamic revolution in 1979, Montazeri became one of the senior leaders of the new administration and was named the heir to al-Khomeini.
The fall out
Montazeri's golden years came to an end in 1989. Over the two preceding years, Montazeri had strongly protested against the mass executions of political prisoners and criticised the Islamic system in Iran.
He urged al-Khomeini to review to the policies of the state and take steps to rectify any problems within them.
But Montazeri's appeal to al-Khomeini incurred but the Ayatollah's wrath, who called the Assembly of Experts for a meeting in February 1989 to discuss Montazeri's remarks.
In March that year, it was announced that Montazeri had resigned his post as heir to the supreme leader.
After al-Khomeini’s death in June 1989, Ali Khamenei, a mid-ranking cleric who rose through the ranks swiftly, became the supreme leader of Iran. Montazeri and his supporters protested the appointment, but they were far weaker than the state’s security, who arrested Montazeri.
Montazeri was placed under house arrest in 1997, but news from his inner circle suggested that he backed the efforts of Iranian reformists to make changes to the country's political system.
He remained largely silent until June this year, when he voiced support for Mir Hossain Mousavi, the reformist candidate in that month's presidential election.
He joined the protests which rejected the results of the polls, which saw Mahmoud Ahmedinajad, the incumbent president, win another term.