Russian opposition politician Alexei Navalny has been removed from the penal colony where he had been imprisoned since the middle of last year and his current whereabouts are not known, his allies said on Monday.

Mr Navalny’s aides have been preparing for his expected transfer to a “special regime” colony, the harshest grade in Russia’s prison system, after he was sentenced in August to an additional 19 years in prison on top of the 11-and-a-half-year sentence he was already serving.

Mr Navalny’s spokeswoman Kira Yarmysh said staff at the IK-6 facility in Melekhovo, 235 km east of Moscow, had told his lawyer waiting outside that the opposition leader was no longer among its inmates.

“Where they have taken him, they refuse to say,” she said on social media platform X, formerly Twitter.

His disappearance comes at the start of the campaign period for a presidential election in which Vladimir Putin confirmed on Friday that he would stand for another six-year term.

Navalny aide Leonid Volkov posted on X that the timing was “0% coincidence and 100% direct manual political control from the Kremlin.”

There was no immediate comment from the Kremlin. Mr Putin and his spokesman make a point of never referring to Mr Navalny by name in an attempt to portray him as politically irrelevant. They say he is treated like any other prisoner.

The process of transferring prisoners by rail across Russia’s vast territory can take weeks, with relatives and family unable to obtain information about their whereabouts and well-being until they reach their destination.

Despite his incarceration, Mr Navalny has often been able through his lawyers to post trenchant attacks on the Kremlin via social media, describing his ordeal behind bars and condemning Mr Putin over the war in Ukraine. But his isolation deepened when three of his lawyers were arrested in October on suspicion of “extremist” activity.