Amnesty International said Thursday that Aleksandr Gabyshev is a "Siberian shaman walking across Russia to Moscow and promising to use his magic powers to 'purge' President Vladimir Putin in 2021."
Speaking in a video on his Instagram account, Gabyshev called Putin "a beast, a fiend of hell, the son of Satan," and said the purpose of his trip to Moscow was to "exorcise" the Russian leader.
Amnesty said armed and masked law enforcement officials "encircled" Gabyshev's camp near the village of Vydrino, in the Russian republic of Buyratia, and "took away the shaman" on Thursday.
Russian state news agency RIA-Novosti, citing local media reports, said supporters of Gabyshev had staged protests over recent elections in Buryatia, and that criminal charges had been brought against the shaman.
Kremlin spokesman Dmitry Peskov said the presidential administration was not aware of Gabyshev's detention and referred questions to local law enforcement.
On Thursday, RIA-Novosti cited the press service of Buryatia's Ministry of Internal Affairs as saying that police had detained a wanted shaman who was going to Moscow, and returned him to Yakutia, the federal Russian republic where the crime was alleged to have been committed.
Yakutia's Ministry of Health said on Friday that Gabyshev had been sent to a psychiatric hospital, where he would undergo tests.
"Aleksandr Gabyshev, a shaman from the Russian republic of Yakutia, began his 8,000km journey to Moscow in March," Amnesty International said in a statement published online.
"Since then, he has covered about 3,000km, attracted many followers and addressed numerous spontaneous public gatherings along the way," the organization added.
"According to eyewitnesses, on the morning of 19 September, armed and masked law enforcement officials encircled the site near the village of Vydrino where Aleksandr Gabyshev was camping with his companions. They took away the shaman without revealing their identities or explaining their actions. His fate and whereabouts are still unknown," the human rights organization said in a statement published online.
Police in Buryatia and Yakutia could not immediately be reached by CNN.