Iran's opposition leaders have called for a day of mourning following the death of Grand Ayatollah Hossein Ali Montazeri, a senior cleric who was a fierce critic of the current government.
Mir Hossein Mousavi and Mehdi Karroubi, two of the defeated candidates in June's disputed presidential poll, urged their supporters to attend the funeral on Monday, according to a statement on Mousavi's Kaleme.org website.
-year-old Montazeri was an architect of the Islamic revolution but fell out with the present leadership.
"Following a call by some grand ayatollahs to mourn the death ... we announce tomorrow, Monday, December 21, a day of public mourning," Mousavi and Karroubi said in a joint statement.
"We invite all saddened religious people mourning the death of this pride of the Shia world to take part in the funeral of this legend of endeavour, jurisprudence and spirituality."
Montazeri will be buried in the shrine of Masoumeh, a revered Shia figure, in Qom, his office said.
"Thousands of people from Isfahan, Najafabad, Shiraz and other cities have left for Qom to take part in his funeral," Parlemannews.ir, the website of the parliament's reformist faction, reported.
"He was the most heavyweight among them [the reformists]. He had great popularity because he was a humble man, he was a simple man ... and above all he was very courageous.
"He didn't fear expressing his views, critical of the current supreme leader or the policies of the government."
"I hope the responsible authorities give up the deviant path they are pursuing and restore the trampled rights of the people," he wrote.
"I hope authorities ... have the courage to announce that this ruling system is neither a republic nor Islamic and that nobody has the right to express opinion or criticism," he said.
Ghanbar Naderi, a journalist for the Iran Daily newspaper, told Al Jazeera: "This is huge blow to the reformist camp, because he is unreplaceable and nobody is happy to hear about his sad demise.
"He used to say that religion should be separated from politics, because in this way, we can keep the integrity of religion intact."
But Seyed Mohammad Marandi, a political analyst at the University of Tehran, told Al Jazeera in August that Montazeri has been "saying the same thing for around 25 years".
"He is not a major player and has always been very critical," Marandi said.
"He was an accomplished theologian and a prominent teacher who spent a large part of his life for Imam's [Khomeini's] cause," he said in a statement carried by state television's website.