MOSCOW — A criminal libel trial alleging Russian opposition leader Alexei Navalny defamed a World War II veteran was adjourned Friday after more than 10 hours of testimony in what Navalny has called a trumped-up attempt by the Kremlin to further smear him.

The 44-year-old Navalny returned to Russia last month after recovering under medical care in Germany from a near-fatal poisoning in August, which Navalny has said was an attack ordered by President Vladimir Putin. Navalny was jailed immediately upon arriving in Moscow on Jan. 17, sparking international outrage and mass protests throughout the country.

Navalny said Friday’s libel case was an attempt to erode his domestic support by pitting him against a member of Russia’s most-treasured generation: World War II veterans. Navalny accused the state of using the 94-year-old veteran, Ignat Artemenko, like “a doll on a chain.”

The trial, which started Feb. 5, is to resume Tuesday.

Navalny was sentenced this month to two years and eight months in a penal colony for alleged probation violations, but his lawyers have said he doesn’t face additional jail time on the libel charge. A fine is expected if Navalny is found guilty.

Even before the proceedings Friday, Russian state media used the case to attack Navalny’s image. The Sunday show “Vesti Nedeli,” or “News of the Week,” described Navalny as a Nazi, adding, “Spitting on the Victory, its victims and their heroism has basically become his style.”

The libel case involves a propaganda video aired in June on the Kremlin mouthpiece RT promoting a nationwide vote on changes to the constitution enabling Putin to stay in office until 2036. The changes were passed in July.

In the video, Russian celebrities and sports figures supported the amendments. Navalny tweeted that the participants were “traitors,” “people with no conscience” and “corrupt lackeys.” Among them was Artemenko.

Russia’s Investigative Committee said the comments contained “deliberately false information denigrating the honor and dignity” of the World War II veteran.

Elena Lukyanova, a law professor at Moscow’s Higher School of Economics, told the Echo of Moscow radio program this week that “legally, this is absolute nonsense.”

“Navalny is absolutely not guilty of anything before the veteran because he did not insult the veteran personally,” she said. She added that Navalny’s comments referred to groups of people recording videos in support of the constitutional changes rather than any individuals.

At the Feb. 5 session, Artemenko, who testified over video link, said he fell ill at one point, and Judge Vera Akimova later reported that he had had to call an ambulance.

Artemenko did not appear Friday, instead submitting a written statement that blamed Navalny’s “constant insults” for his ill-health.

Navalny called the Artemenko letter an “obvious forgery.” Navalny later told Igor Kolesnikov, Artemenko’s grandson and a witness in the case, that he wanted to know how Kolesnikov “wound up on the slippery slope of trading your own grandfather.”

Akimova, the judge, advised Kolesnikov not to answer.

Although Navalny has said the charges against him are an attempt to silence him and intimidate his supporters, his repeated appearances in court — this was his fifth since returning to Russia less than a month ago — have given him opportunities to denounce Putin as well as mock Russia’s judicial system. Navalny also faces a separate case in which he is accused of embezzlement and could be sentenced to up to 10 years.

On Friday, he attacked the very amendments that Artemenko supported in the RT video in June, saying “everyone involved in these constitutional changes are stooges and traitors,” according to media in the courtroom.

“I think this video is hideous, rotten, lying, and disgusting,” Navalny was quoted as saying. “I saw this video and thought, ‘Ah, Russia Today has joined the campaign to deceive as many Russians as possible by pimping out these people’s faces.’”

During a recess, Navalny asked prosecutor Yekaterina Frolova how many witnesses she had.

“Four. And you?” she replied.

“We have the whole world as witnesses to your lies,” he said.

Concurrent to this latest case against Navalny, the European Union has discussed levying sanctions against Russia for its treatment of the Kremlin critic. Russia’s Foreign Ministry has criticized Western diplomats attending Navalny’s hearings; spokeswoman Maria Zakharova said their presence was evidence of trying to interfere in Russia’s affairs.

Foreign Minister Sergei Lavrov said Friday that “we’re ready” for a breakup with the European Union, according to excerpts of an interview with state media posted on the ministry’s website.

“If we see yet again, just like we have felt before on multiple occasions, that sanctions are imposed in certain areas and create risks to our economy, including in the most sensitive areas, then yes,” Lavrov said. “We don’t want to be isolated from international life, but we should be prepared for that.”