Millions of Iranians are mourning the death of Grand Ayatollah Hossein Ali Montazeri who is due to be buried in the holy city of Qom on Monday. 

Montazeri, who died on Sunday aged 87, was one of the architects of Iran's Islamic Revolution but eventually became one of the government's fiercest critics.

Montazeri's stance against Iran's leadership made him a hero of the country's opposition, while his criticisms were all the more stinging because of his stature as one of Shia Islam's most revered clerics.