Mikhail Khodorkovsky, the Russian oil billionaire, denounced the government's legal campaign against him on Friday as "extremely dangerous" for society, giving his first detailed response to the charges that have kept him in prison for nearly nine months.

In a loud, confident voice, Russia's richest man opened his courtroom defense with a point-by-point rebuttal of the allegations, ridiculing them as "baffling," "sloppy and groundless" and "a politically motivated, selective exercise of justice." In a country where wealth is still suspect, he cast himself as a scapegoat in the hunt for culprits from the often corrupt sell-off of state assets during the 1990s.

"I intend to prove that this is an awkward attempt to write off the mistakes made in the privatization legislation at the beginning of the privatization process," Khodorkovsky told the three-judge panel hearing the case. He spoke from a metal cage, as is standard for defendants in Russian courtrooms.

Khodorkovsky's first extended statement on the case since his arrest at gunpoint last October in Siberia was the most dramatic moment so far in the biggest trial of the post-Soviet period. While the 227 binders of evidence dwell on the details of stock transactions and tax shelters, many Russians feel that larger issues -- the country's relationship to capitalism after 13 years of fitful experimentation, and the boundaries between state and private power in the new era -- are at stake in the trial.

Dressed in a black V-neck pullover and blue jeans, his graying hair shorn close, Khodorkovsky, 41, portrayed himself as only the latest victim of repression in a country with centuries of experience in it. "The demonstration of force indifferent to the law, albeit going through the motions of observing its procedures on the surface, is extremely dangerous for the prospects of development of our country," he said.

His billionaire partner and co-defendant, Platon Lebedev, put the argument more starkly in his statement. "I've come to realize that the state is repressing me for political . . . reasons, on charges invented or craftily organized," he said.

The government dismissed the defense as political puffery by suspects clearly guilty of elaborate swindles. "I must give credit to Mikhail Khodorkovsky and Platon Lebedev," prosecutor Dmitri Shokhin responded in court. "They can quite skillfully juggle with facts." He went on to chide the pair for "making loud statements" intended to fog the truth and influence the media and public opinion.

With opening statements on both sides concluded, the trial will resume Tuesday when prosecutors begin presenting evidence and calling witnesses. Lawyers expect the trial to last three to four months as the two sides debate whether Khodorkovsky and Lebedev cheated the state of more than $1 billion through crooked privatization and tax evasion schemes. If convicted, they each face 10 years in prison.

In a parallel civil proceeding, the state has begun pulling apart Khodorkovsky's main firm, Yukos Oil Co., Russia's largest oil producer. Government agents have launched the legal process of seizing company assets to satisfy retroactive tax assessments totaling nearly $7 billion, rejecting any proposed compromise.

Khodorkovsky's defenders do not assert that he was the most ethical entrepreneur in the rough-and-tumble world of 1990s Russian capitalism. Some privately acknowledge that he may have done what prosecutors allege. But he was not much different from many other tycoons of the period, they argue, and yet he was the only one targeted -- and only after he began to challenge President Vladimir Putin's monopoly on power by, among other things, funding reformist opposition groups.

At the same time, the Putin government's pursuit of Khodorkovsky, which started several months before parliamentary elections, remains popular with many Russians resentful of the handful of politically connected men who amassed enormous fortunes virtually overnight.

"Anyone can be a dissident, even a billionaire," said Alexei Makarkin, a political analyst at the Center for Political Technologies, a Moscow research group. "Is he looked upon as a dissident? In this respect, Russian society has split. Logically, he is a dissident, but in the eyes of most Russians, he's not."

Until Friday, Khodorkovsky had said little in public since his arrest, beyond pleading not guilty and offering a comment or two about his health or his company during breaks in proceedings. In the spring, he issued two letters from prison in which he lamented the "crisis of liberalism" in Russia and acknowledged that the excesses of the privatization era had discredited the notion of democracy in many eyes.

In his statement in court Friday, Khodorkovsky focused more on the specifics of the charges than their political overtones. "Society has already evaluated whether this process is a political one or not. This is obvious," Genrikh Padva, one of his attorneys, said outside the faded yellow-brick courthouse in northern Moscow after the day's hearing. "That's why he didn't think he should discuss this in detail."

At the heart of the case against Khodorkovsky and Lebedev is the 1994 state auction of a 20 percent share in a fertilizer company called Apatit. Prosecutors allege that Khodorkovsky's team rigged the sale so that only its own front companies competed against its bid. Then, once the stake was secured, prosecutors charge, Khodorkovsky and his partners failed to invest the $283 million they were required, under the terms of the auction, to invest in the firm.

In the 1990s, the government filed a civil complaint against Khodorkovsky's team concerning the transaction, later settling it with a $15.5 million fine. Russia's chief prosecutor, Vladimir Ustinov, approved that agreement last year, determining that there were no grounds for prosecution. But Ustinov abruptly reversed gears two months later, after Khodorkovsky angered the Kremlin with his political activities.

Prosecutors accuse Khodorkovsky of perpetrating similar fraud in the 1995 privatization of part of a fertilizer research institute called NIUIF. They also allege that he avoided paying hundreds of millions of dollars in personal and corporate taxes by registering as a consultant and setting up an elaborate system of transferring profits to companies in low-tax zones.

In his statement Friday, Khodorkovsky dismissed the fraud charges as "illogical." In the privatization cases, he said, the state in effect accuses him of "refusing to take money out of my one pocket and put it into my other pocket" by not investing in his new companies.

With regard to the taxes, he said Yukos employed only legal tax shelters and was still the country's second-largest taxpayer. "How can it be that a company that formed 5 percent of the federal budget suddenly is supposed to have paid twice as much?" he asked.