MOSCOW -- On Tuesday, Alexei Navalny's allies in prison proclaimed that the Kremlin critic was missing from the prison where they were serving his sentence.

His close associates believe he is being transferred into another prison. However, in Russia, prison transfers can take days or even weeks and are kept secret.

"All the time that we don’t know where Alexei might be, he’s left alone with a system that once tried to kill his life," Kira Yarmysh, Navalny's spokesperson, said via social media.

Leonid Volkov (Nathaniy's closest ally), stated on Telegram that Navalny's lawyer visited him in prison on Tuesday to learn that there was no such convict.

Volkov stated, "Where Alexei is right now and to which prison he's being taken to, we don’t know."

Navalny was the most determined political foe to Russian President Vladimir Putin. He was returning from Germany in January 2021, where he was recovering from nerve-agent poisoning. He was sentenced to a 2 1/2-year sentence for parole violation.

Navalny was sentenced in March to nine years imprisonment for fraud and contempt for court. He dismissed these charges as politically motivated and a bid by the authorities to keep him behind bars as long as possible.

The judge sentenced the Kremlin critic in a maximum-security prison. After he lost his appeal, he was to be transferred to one.

This conviction came after a year-long Kremlin crackdown against Navalny's supporters and other opposition activists. Authorities seem eager to suppress all dissent.

Navalny's associates were charged with criminal offenses and many fled the country. His political infrastructure, which included an anti-corruption foundation as well as a network of regional offices across the country, was destroyed when he was labeled an extremist group.