* Activist complains of prison torture
* Says guards and governor systematically beat him
* Kremlin says Putin will be informed

A Russian opposition activist who became the first person to be jailed for repeatedly staging peaceful anti-Kremlin protests under a new law says he is being tortured in prison and fears for his life.

A Moscow court sentenced Ildar Dadin to three years in prison in December for holding a series of one-man protests in a case Amnesty International called "a cynical attack on freedom of expression." His jail term was later reduced to two and a half years on appeal.
Russian rights activists regard Dadin, an outspoken critic of President Vladimir Putin and his policies, as a political prisoner. The authorities say Dadin broke a law, which was introduced after big anti-Kremlin protests, that criminalises anyone who violates protest rules more than twice in 180 days.
In a letter to his wife from prison in north-west Russia published by online news portal Meduza on Tuesday, Dadin, 34, said he was being subject to group beatings where around 10 prison guards would kick him at the same time.
He said he had also had been hung up like a piece of meat with his hands handcuffed behind his back, that he had been stripped and threatened with rape, and that the prison governor had warned him he would be murdered if he complained.
"Regular beatings, bullying, humiliation, insults, intolerable detention conditions - this is happening with the other prisoners, as well," the letter said.
"If I am again subjected to torture, beatings, and rape, it is unlikely that I will last more than a week."
Anastasia Zotova, his wife, said on social media she had felt something was wrong when the prison authorities did not allow her to speak to her husband on the phone or to visit.
When asked about the allegations, Dmitry Peskov, a spokesman for Putin, told reporters that the Russian leader would be informed about Dadin's letter.
"This is a case which merits the closest attention of the relevant authorities, in this case the prison service," said Peskov.
Local investigators and the prison service have said they will investigate Dadin's allegations, Russian news agencies reported.
Dadin told his wife he feared he might be murdered to shut him up.
"In case of my sudden death, you may be told that I committed suicide, had an accident, was shot while trying to escape, or (died) fighting with another prisoner," he wrote.
"But this would be a lie."