Jailed Russian human rights activist Oleg Orlov was asked to sign a form saying he was willing to fight in Ukraine despite the fact he is 70, his organization said on Friday.

Orlov, a leader of the rights group Memorial that won a share of the Nobel Peace Prize in 2022, was sentenced last month to 2-1/2 years in prison for "discrediting the armed forces" after he took part in anti-war demonstrations and published an article in which he said Russia had descended into fascism.

Memorial said Orlov was asked in the detention center where he is currently held to sign a form saying he was willing to take part in Russia's "special military operation" in Ukraine. It did not specify who asked him to do so.

Orlov "inquired with a laugh if they weren't bothered about his age - this year he will be 71. They replied they weren't bothered about anything," Memorial said.

"Orlov, of course, wrote: 'I don't agree.'"

Tens of thousands of Russian prisoners have been enlisted to fight with the Russian army or as mercenaries in Ukraine since the start of the war two years ago. It was not clear if the invitation to Orlov was intended seriously or as a form of intimidation.

Reuters has requested comment from the Russian prison service.

Memorial, founded in 1989 to document human rights abuses in the Soviet Union, has decried the case against Orlov as an attempt to "drown out the voice of the human rights movement in Russia."

It said he was getting used to life in a small cell with 10 other people and that his fellow inmates were treating him with respect and addressing him as "batya," an affectionate word for father.