An influential pro-reform ex-president criticized the country's first trial of activists and protesters following the disputed presidential election as a sham that would further erode confidence in the ruling Islamic establishment.

Mohammad Khatami said he hoped the "show" trial of more than 100 people that started Saturday would not "lead to ignorance of the real crimes" carried out by authorities following the June 12 vote, including alleged abuse and murder of detainees.

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The opposition has sought to capitalize on growing criticism from both conservatives and reformists of the government's violent crack down against the hundreds of thousands of people who took to the streets following the election to protest hard-line President Mahmoud Ahmadinejad's disputed victory.

At least 20 people were killed in the unrest that followed the vote, although human rights groups believed the number is far greater and at least one person has died while in government detention.

The mass trial is part of the government's efforts to choke off the protest movement by targeting key supporters of Mir Hossein Mousavi, the opposition leader who claims he was the true election winner. The defendants include some of the most prominent reformist politicians, including Khatami's former vice president, Mohammad Ali Abtahi.

The government used Saturday's hearing to press its claims that the opposition was a tool of foreign countries seeking to topple the Iranian government.

State media quoted Abtahi and others as confessing to working together to foment unrest. But rights groups have said such confessions are often obtained under duress in Iran.

"Relying on claimed confessions expressed in this specific situation has no credit," said Khatami, according to a report posted on his Web site, Baran, late Saturday.

The former president, who held office from 1997 to 2005, criticized the court for not allowing defendants' lawyers access to the courtroom or the case files.

"As far as I have learned, what happened in the trial was contrary to the constitution and law, as well as citizens' rights," said Khatami.

Instead of a show trial, Khatami said the public expected the government to "confront the problems and tragedies that happened in some detention centers and apparently led to murder."

Some conservatives joined the chorus of reformists criticizing the government's violent crack down following the death of the son of a prominent member of their camp, Abdolhossein Rouhalamini. Rouhalamini is a close ally of Mohsen Rezai, the only conservative who ran against Ahmadinejad in the election.

His son, Mohsen, who was arrested during a July 9 protest, was taken to a hospital after two weeks and died. The Norooz Web site reported that Mohsen's face was beaten in when his father received the body.

The growing criticism comes only days before Ahmadinejad is to be sworn into a second term and has compounded the biggest challenge the cleric-led government has faced since the 1979 Islamic revolution.