The mother of Ukrainian director Oleg Sentsov, who has refused food for 60 days, has appealed to President Vladimir Putin to free her son as hopes faded that the Kremlin critic would get out of a Russian prison alive.
Lyudmila Sentsova's letter to Putin was released on Friday, the day the hunger-striking Ukrainian activist and filmmaker turned 42 in a jail in the far north of Russia.
"I ask you, Vladimir Vladimirovich, to show mercy and grant pardon to Oleg Sentsov, do not destroy his life and that of his loved ones. We are waiting for him at home," she said in the letter dated June 22.
"He has already served four years. His children are waiting for him. His younger son suffers from autism. They are feeling bad without him. They will never be happy without their father."
Sentsov is serving a 20-year sentence after being convicted on terrorism charges over an alleged arson plot in Crimea. His supporters say the case was trumped up.
Sentsova said her son had not killed anyone, describing him as a man interested in film-making.
The vocal Kremlin critic was detained in Crimea in 2014 after Russia annexed the peninsula from Ukraine.
Western governments and celebrities have repeatedly urged the Kremlin to release Sentsov. Prominent Russian filmmaker Alexander Sokurov asked the Pope to intervene.
But Moscow has shown little enthusiasm for letting the anti-Kremlin filmmaker go and hopes are quickly fading that he will be released by the time the World Cup Russia is hosting ends on Sunday.
The Kremlin has said Sentsov should himself ask Putin for a pardon for his request to be considered. Sentsov has refused to do so.
Ukrainian President Petro Poroshenko said on Facebook his government would keep up pressure on the Russian authorities in a bid to free Sentsov and dozens of other Ukrainians it considers political prisoners.
The director and author launched his hunger strike on May 14 to demand Russia release Ukrainian political prisoners.
He has timed his protest to coincide with the World Cup to attract maximum attention to the plight of Ukrainians imprisoned in Russia.
Sentsov has lost around 15 kilogrammes, being sustained by water and a glucose drip, his relatives say.
On average, humans can survive without food for about eight weeks.
Russian activists who staged pickets in Sentsov's support have been harrassed by the authorities.
On Friday, an activist was sentenced to five days in jail for demonstrating in his support in the second city of Saint Petersburg, officials said.
Sentsov is best known for his film "Gamer", which screened to critical acclaim at the Rotterdam Film Festival in 2012.
Supporters say Russia wanted to make an example of him with the stiff sentence on charges of masterminding arson attacks, which he denies.