MOSCOW — The legal troubles of Aleksei A. Navalny, Russia’s most high-profile opposition leader, continued on Thursday with a court in Moscow fining him the equivalent of almost $5,000 on charges of organizing a public event without permission from the authorities.

The court also fined two of Mr. Navalny’s associates, Leonid M. Volkov, the chief of staff of his unsanctioned run for the Russian presidency, and Nikolai N. Lyaskin, the coordinator of the campaign’s Moscow branch.

Mr. Navalny is seeking to take part in next year’s presidential election, despite being barred from doing so because of an earlier conviction he calls politically motivated. In the meantime, his strategy is to make his exclusion so embarrassing for the Kremlin that he is permitted to run.

In March and June, he organized nationwide anticorruption demonstrations attended by tens of thousands of protesters, many of them young people. In both cases, he was arrested and jailed for days.