Maria Alyokhina, 24, who is serving a two-year sentence for the group's anti-Vladimir Putin performance in Russia's main Orthodox Cathedral, was moved to a "safe" place in the prison camp in the Perm region, an official with the regional prison service told AFP.
"Alyokhina was moved to a safe place from the general unit on Wednesday evening after she wrote a letter to the prison authorities asking to be transferred," he said.
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"The reason for the move is that she has poor relations with other prisoners," he said, without elaborating.
Alyokhina, who was transferred to the remote Berezniki prison camp in Perm last month, will remain isolated from other inmates for three months unless she requests to be moved back, the prison official said.
"After that the prison administration will think of what to do next," he said.
Tabloid Komsomolskaya Pravda said Friday that Alyokhina complained to her relatives over the phone that other prisoners were making threats against her and asked rights organisations to support her.
Alyokhina and fellow band member Nadezhda Tolokonnikova were sentenced in August to two years in prison for hooliganism motivated by religious hatred after they performed a "punk prayer" in a Moscow cathedral last February.
Bandmate Yekaterina Samutsevich was released on appeal with a suspended sentence because guards grabbed her before she could take part in the performance. Tolokonnikova is serving her sentence in another colony in central Russia's Mordovia region.
Amid some controversy, the jailed women this week fired their high-profile legal team and hired other lawyers, notably one who helped free Samutsevich.
Unlike the initial defence trio, who frequently commented on the case on Twitter, their new attorneys have spoken little about their defence strategy.
Pyotr Verzilov, who is Tolokonnikova's husband, told AFP that a lawyer from Perm met with Alyokhina Friday, and confirmed that she was moved to a solitary cell after a conflict with other inmates.
"Some inmates told her she has to go on hunger strike," he said. "She was surprised, and they started behaving aggressively." He added that Alyokhina "feels well" and some of her relatives were planning to visit her Monday.
Alyokhina, who has been apart from her five-year-old son Filipp since her jailing in March, emerged as the most outspoken of the group during the trial, frequently cross-examining witnesses and arguing with the judge.
Russian authorities have come under fierce criticism for jailing the women over a song in which they asked the Virgin Mary to "get rid of Putin".
President Vladimir Putin called the sentence fair, and said the girls were asking for it when they held their performance. "One cannot undermine the moral foundations" of Russia, he said of the case last month.
The case also created a deep rift between Russian society and the Orthodox Church, with rallies, sometimes violent, held both for and against the girls, and Orthodox activists staging public prayers next to the courthouse.
