A jailed member of Russia's punk band, Pussy Riot, has been moved to a solitary confinement cell after she went on hunger strike to protest against what she called "slave labour" at the prison.

Nadezhda Tolokonnikova, who has been imprisoned for two years over a "Punk prayer" protest against Vladimir Putin in a Moscow cathedral in August 2012, was moved into isolation on Tuesday.

The head of a public supervising committee in the remote region where she is confined, Gennady Morozov, denied the transfer was punishment. He described her cell as a "safe place" where she would be shielded from threats from fellow inmates.

He said Tolokonnikova's allegations that she had received death threats from a senior prison official and of deplorable conditions at Corrective Colony No. 14 in the Mordovia region, southeast of Moscow, would be investigated.

She could face discipline for slander, if they were found to be false, he added.

Spacious cell

A spokeswoman for the Federal Prison Service said the member of the feminist punk rock group is now in a spacious single cell with a bed, a refrigerator, toilet and personal belongings.

In a letter circulated by her husband, Tolokonnikova said inmates were forced to work up to 17 hours a day sewing police uniforms and were allowed no more than four hours sleep a night.

She said camp officials used senior inmates to enforce order, describing a system of collective punishment and production quotas reminiscent of Soviet-era Gulag labour camps.

When Tolokonnikova appealed for investigation of the conditions, she said a senior prison official told her: "You'll surely never feel bad again because it's never bad in the other world."

Kremlin critics say her sentencing along with other band members is part of a crackdown on dissent since Putin returned to the presidency for a third term in May 2012.

Tolokonnikova is due for release in March, as is fellow band member Maria Alyokhina. A third band member had her sentence suspended.