Iranian hardliners accused opposition leaders of treason yesterday as defeated presidential challenger Mir Hossein Mousavi said the authorities used "mediaeval torture" to force confessions from protesters on trial over the election unrest.

Former president Mohammad Khatami also said Saturday's mass trial of 100 protesters and prominent reformists was against the constitution, putting him at loggerheads with hardliners in an escalating feud between rival factions.

The powerful hardline wing took aim at both opposition leaders, accusing them of trying to lead a "velvet revolution" after the June re-election of President Mahmoud Ahmadinejad and lodging a judicial complaint against Mr Mousavi.

And another 10 people were brought before a revolutionary court yesterday on charges relating to the massive street protests that erupted after Mr Ahmadinejad was returned to power in what the opposition said was a rigged vote.

"Evidence of Khatami and Mous-avi's treason unveiled," thundered the headline in the hardline Kayhan newspaper.

"The plot leaders are corrupt people whose unforgiveable crimes include killing innocent people and cooperating with foreign enemies," it said.

"If the main instigators of unrest who are known are not confronted, they will continue conspiring."

A group of hardline MPs stepped up the pressure on the opposition, filing a complaint against Mr Mousavi to the judiciary, the Fars news agency said.

"Those who issued statements and directed recent riots should be accountable for the bloodshed and go on trial," said Mohammad Taghi Rahbar, a hardline member of Parliament's judicial commission.

But Mr Mousavi remained defiant and said confessions at Saturday's trial were extracted by torture.

"The scenes that we saw were a clumsy preparation for the launch of the 10th government," Mr Mousavi said on his website about the trial, held just days before Mr Ahmadinejad is to be sworn in on Wednesday.

"They expect a court, which itself is fraudulent, to prove that there was no fraud committed in the election," said Mr Mousavi.

"What are they trying to convince people of... (by) relying on confessions which obviously bore the hallmarks of mediaeval-era torture?"

His comments came after some reformists, including a prominent Khatami aide, made a dramatic climbdown at the trial, saying Mr Ahmadinejad's victory was clean and that they had been pushed into demonstrating against the results.

Mr Khatami also denounced the trial, the first since Mr Ahmadinejad's re-election set off the worst crisis in the 30-year history of the Islamic republic and exposing deep differences among the ruling elite.