Imprisoned Russian opposition leader Alexei Navalny on Tuesday lost an appeal contesting the decision by penitentiary officials to label him as "inclined to commit crimes of a terrorist or extremist nature."

Navalny, who has been behind bars since January 2021, was first designated by the penitentiary authorities as a flight risk, which implied additional checks and inspections in prison. But in October last year officials replaced that label with the "terrorist or extremist" one.

"I was worried they would demand that I kissed portraits of [President Vladimir] Putin and learned quotes by [his top associate Dmitry] Medvedev, but it wasn't necessary. It is just that my bunk bed now has a label that describes me a terrorist," Navalny, in his usual sardonic matter, commented on the move at the time in a social media post.

He and his defense team filed an appeal contesting the label, but a panel of judges in the Russia's Vladimir region about 62 miles east of Moscow on Tuesday rejected the appeal and ruled to keep the designation in place.

Navalny, Putin's fiercest foe, was arrested in January 2021 upon returning from Germany, where he had been recuperating from nerve-agent poisoning that he blames on the Kremlin, and handed a 2½-year sentence for a parole violation.

In March, Navalny was sentenced to nine years in prison on fraud and contempt of court charges that he rejected as politically motivated. The move signaled an attempt by the authorities to keep him behind bars for as long as possible.

The new sentence followed a year-long Kremlin crackdown on Navalny's supporters, other opposition activists and independent journalists, in which authorities appear eager to stifle all dissent.

Navalny's close associates have faced criminal charges and left the country, and his group's political infrastructure — an anti-corruption foundation and a nationwide network of regional offices — has been destroyed after being labeled an extremist organization.

Navalny and several of his associates have been added to Russia's registry of terrorists and extremists.