Russian prison officials have been accused of burning copies of the Koran and assaulting Muslim prisoners, a migrants' organisation in Russia says.
The People's League of Tajiks said the incidents happened at a jail in the Tambov region, south-east of Moscow.
It said prison officials had also destroyed a mosque set up by inmates.
The organisation said four prisoners from Tajikistan, two from Uzbekistan and one from Kyrgyzstan had complained that they were assaulted by guards.
The group called on the Russian justice ministry and state prosecutors to investigate the accusations.