About 100 leading Iranian reformists went on trial on Saturday, accused of trying to topple the clerical establishment by orchestrating mass protests after the disputed presidential election, Iranian media reported, according to Reuters. The mass trial, whose timing was not announced in advance, opened four days before President Mahmoud Ahmadinejad is inaugurated for his second term in parliament on Wednesday. The defendants include former ministers, a former vice-president and lawmakers arrested after the street protests that erupted in June after Ahmadinejad was declared to have won an overwhelming victory over moderate former prime minister Mirhossein Mousavi. The vote plunged Iran into its biggest internal crisis since the 1979 Islamic revolution and exposed deep divisions in its ruling elite. Iranian media have reported the deaths of 20 protesters since the vote. The authorities rejected opposition accusations of vote-rigging and Iran's supreme leader, Ayatollah Ali Khamenei, has endorsed Ahmadinejad's re-election. After his inauguration, the president will have two weeks to introduce his choice of ministers for approval by parliament, but there are signs of growing opposition to Ahmadinejad even among his staunchest supporters. State television coverage of the courtroom showed many young defendants, some handcuffed, and former vice-president Mohammad Ali Abtahi, former deputy foreign minister Mohsen Aminzadeh and former MP Mohsen Mirdamadi, leader of the biggest reformist party, the Islamic Iran Participation Front, in prison uniform. "The trial of some of those accused of being involved in post-election unrest started this morning," the official IRNA news agency said. "Some 100 people were put on trial in a Tehran Revolutionary court." The hardline semi-official Fars news agency said Abtahi had admitted that the opposition allegations of election fraud had only been a pretext designed to trigger mass protests. Also on trial are other prominent members of Iran's leading moderate parties, founded by former presidents Akbar Hashemi Rafsanjani and Mohammad Khatami, both backers of Mousavi. IRNA said the charges included acting against national security by planning unrest, participating in a "velvet revolution", attacking military and state buildings and conspiring against the ruling system. "Velvet Revolution" was the name given the non-violent 1989 revolution in Czechoslovakia that overturned communist rule. Iran's leaders have frequently accused the United States of trying to topple clerical rule in Iran through cultural change. Under Iran's Islamic law, acting against national security, a common charge against dissenting voices, could be punishable by the death penalty. Rights groups say hundreds of people, including senior pro-reform politicians, journalists and lawyers, have been detained since the election. The indictment said: "These parties planned, organised and led the illegal gatherings and riots," IRNA reported. It also said the Participation Front, the main pro-reform party set up by Khatami, had "had contacts with a British spy". The party rejected the charges, saying: "After 50 days of isolating and pressuring the detainees ... such a weak indictment has been prepared ... It is a politically motivated and illegal indictment." Iran accuses Western countries, particularly Britain and the United States, of supporting and encouraging the protesters. Western countries deny this and Mousavi on Saturday also rejected the accusation. "The protests since the election were not linked to foreigners at all ... Iranians' rights have been violated at the election," Musavi's website Ghalamnews quoted him as saying. The Fars agency said at least four prominent reformers now say the vote was not rigged. "Former vice-presidents Mohammad Ali Abtahi and Mohsen Safai-Farahani, former Industries Minister Behzad Nabavi, (Iranian-Canadian journalist) Maziar Bahari and former deputy interior minister Mostafa Tajzadeh have confessed that the issue of fraud in the Iran vote was baseless," it reported. Iran freed 140 detained protesters on Tuesday, while 250 others remained in jail.