Imprisoned Russian opposition politician Alexei Navalny

Aleksey Anatolyevich Navalny (Russian: Алексей Анатолиевич Навальный) said today that prison authorities have transferred him to solitary confinement for the second time this month.

Navalny is serving a sentence that, according to him, is based on false charges, BTA reported.

Russia's fiercest critic of President Vladimir Putin is serving 11-and-a-half years behind bars after pleading guilty to charges of violating probation, fraud and contempt of court.

The opposition politician claims that all the charges against him are fabricated as a pretext to suppress dissent and thwart his political ambitions.

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In a post on his Twitter and Instagram accounts, each of which has millions of followers, Navalny wrote through his lawyers that he was sent to solitary confinement for five days for briefly moving without holding his hands behind the back, which is against prison rules.

"If things continue like this, this will become my permanent residence," wrote the 46-year-old oppositionist, calling the cell "hell's closet."

He added: "The order obviously came from Moscow. Even by the standards of a Russian prison, to send someone to solitary confinement just because they didn't keep their hands behind their back for 3 seconds is too much."

The federal service in charge of prisons in Russia has not yet commented on this information.

Navalny, who was transferred to a stricter prison colony east of Moscow in June, said on August 15 that he was thrown into a solitary confinement cell for failing to fasten the top button of his prison uniform, which he claimed it's small for him.

Last year, Navalny voluntarily returned to Russia from Germany, where he was treated after, according to Western labs, a near-fatal attempt to be poisoned with a Soviet-era nerve agent in Siberia.

Russia denies trying to kill him.

Alexei Navalny