Imprisoned Ukrainian filmmaker Oleh Sentsov, who ended his nearly five-month hunger strike in a Russian prison in early October, is feeling "much better than a month ago," a prominent Russian rights activist says.

Nikolai Shchur, an outspoken critic of the Russian prison system, wrote on Facebook on November 1 that he received a letter from Sentsov, dated October 29, in which the film director says he had "survived" the ordeal.

"The test results are still not so good, but not as bad as they were before,” Shchur quotes Sentsov's letter as saying. “So, do not worry too much about me -- I have survived."

The letter could not be independently authenticated, but Shchur, a well-known activist in Russia's Chelyabinsk region, has in the past received correspondence from Sentsov.

Sentsov, a Crimean native who opposed Russia's 2014 takeover of the Ukrainian peninsula, is serving a 20-year prison term after being convicted of terrorism in a trial that he, rights groups, and Western governments contend was politically motivated.

Imprisoned in Russia's Far Northern Yamalo-Nenets region, Sentsov started the hunger strike on May 14, demanding that Russia release 64 fellow Ukrainians he considers political prisoners.

He ended his protest on October 6, saying he had to do so to avoid being force-fed by prison authorities.

Sentsov's cousin, Natalya Kaplan, said on October 16 that Sentsov might not survive after ending the hunger strike because of damage to "almost all his organs," including liver, heart, and brain.

On October 25, the European Parliament awarded Sentsov its prestigious 2018 Sakharov Prize for Freedom of Thought.

With reporting by Hromadske