MOSCOW — A Moscow book fair has prompted accusations of censorship after it canceled an appearance by a debut author who is a top aide to jailed opposition politician Aleksei Navalny.

Kira Yarmysh, Navalny’s longtime spokeswoman and a prominent activist in her own right, was set to present her novel Incredible Incidents In Women’s Cell No. 3 at the Non/Fiction book festival, which will be held at an exhibition space near the Kremlin from March 24 to 28.

But the book’s publisher, Corpus, revealed that its parent company had given in to pressure by the event’s organizers to withdraw Yarmysh’s appearance from the event.

“It’s the typical argument,” Corpus chief editor Varvara Gornostayeva wrote in a Facebook post on March 23. “We need to preserve the book fair at any price, and an appearance by a opposition figure, and Aleksei Navalny’s spokesperson at that, places the fair’s existence under threat.”

Vitaly Kogtyev, a representative of the book fair, confirmed the decision to withdraw Yarmysh’s invitation in comments to Russian media, though he did not cite a reason. Non/Fiction did not immediately respond to a request for comment, but the event program published on its website includes no mention of Yarmysh or her book.

The controversial decision comes at a tense time for Russia’s opposition, and specifically Navalny and his regional network of campaign offices. The anti-corruption crusader incited a nationwide wave of protests in January that was brutally suppressed by police, and on February 2 he was sentenced to 2 1/2 years in prison over a parole violation charge he contends is absurd.

Since his return to Russia in mid-January after five months in Germany recovering from the effects of a nerve-agent poisoning he blames on President Vladimir Putin, Navalny’s movement has faced a targeted campaign against its activists and coordinators throughout Russia, some of whom are in custody or face criminal prosecution in connection with rallies.

Last week, Navalny’s award nomination for a series of investigative documentaries revealing evidence of corruption among the country’s top officials prompted a bitter conflict in Russia’s filmmaking community and led the Russian Guild of Film Critics to drop its prestigious cinema prize.

Yarmysh’s book, about six women who share stories while stuck in a jail cell, came out in the fall. Since February 2, she has been under house arrest pending trial on charges that she and nine other defendants created a risk to public health by promoting the January protests.

On March 18, a Moscow court extended her confinement by another three months, rendering her incapable of attending the scheduled book presentation even if it had gone ahead.

Yarmysh faces up to two years in prison if she’s convicted, and she is banned from communicating online. But in a post to her Facebook account, published by her aides, she issued a scathing assessment of the decision, calling it “base and cowardly” and a case of “direct collaboration with the authorities.”

“Censorship and self-censorship are among the worst traits of authoritarianism,” she wrote. “This can’t be explained with any virtuous intention to ‘save the book fair’…. On the contrary, silent tolerance of a division between permitted and prohibited writers is what will sooner or later destroy it.”