Aleksei A. Navalny, the most prominent challenger to the rule of President Vladimir V. Putin of Russia, appeared at a court hearing on Tuesday to face charges of embezzlement and contempt of court that could extend his imprisonment by 15 years.
The trial is starting as Mr. Putin has grabbed the world’s attention by engaging in a high-stakes standoff with the West over Ukraine. Mr. Navalny’s supporters said they believe the trial was deliberately scheduled to coincide with the crisis to divert attention away from his case.
The proceedings were held in a prison outside Moscow, where Mr. Navalny, who has accused Mr. Putin of ordering his security agencies to assassinate him, is serving a sentence that ends next year. The Kremlin has denied Mr. Navalny’s accusations.
Standing in a makeshift courtroom in his prison uniform, Mr. Navalny accused the court of deliberately holding the trial in a penal colony hours away from Moscow to reduce media attention and obstruct the work of his lawyers, who were not allowed to bring their laptops with case materials.
“People who have ordered this trial are fearful,” said Mr. Navalny, according to MediaZona, a Russian news site. “They are fearful of what I say here, that people will see that the trial was clearly fabricated.”
Russian investigators have accused Mr. Navalny of embezzling $4.7 million in donations to his foundation. In a video published ahead of the trial, Mr. Navalny’s ally Ivan Zhdanov accused two of the four victims mentioned in the case of cooperating with the Russian government to “slander an innocent person in exchange for money.”
“These are people who were brought by the hand, given someone else’s money and told to make one payment,” said Mr. Zhdanov, adding that the criminal case was opened only a day after one of the four victims sent a donation to the foundation.
The other two people who pressed charges against Mr. Navalny were pressured to do so, Mr. Zhdanov said. One is facing up to 10 years in prison, and the other had been under investigation over tax evasion, he said.
Mr. Navalny was arrested for violating parole at a Moscow airport after returning to Russia last year from Germany, where he was recovering from poisoning he said was organized by the Russian government. Ever since his return and subsequent sentencing, Mr. Navalny and his associates and supporters have faced increased pressure from the Russian government.
Multiple criminal cases were opened against him and his allies. His anticorruption foundation and his political organization were declared extremist. Many of his allies had to flee Russia. Some were arrested and remain in custody.
“Since I insulted your Putin not only by surviving, but by returning, that means that I will be in prison, there will be this case,” Mr. Navalny told the judge and prosecutors during the hearing, according to Zona Media. “The real crime I could commit is if I get afraid of you and who stands behind you.”
