Prison officials say Rim Shaigalimov, 52, committed suicide, but his relatives think he was killed.
His wife, Lyudmila Shaigalimova, told RFE/RL that his death "must have been an order from above." She added that the officials “can assert what they will -- that it was an accident or whatever, but that’s a lie. He was killed."
Shaigalimova said she and her family saw his body at the mortuary. "It was absolutely clear that the death was caused by suffocation," she said.
She said no prison officials had time to meet with her or other family members to discuss his death.
Shaigalimov was serving a five-year sentence in Krasnoyarsk Krai for fighting with a police officer. He had been in prison for seven months.
Shaigalimov was one of the leading Other Russia activists in the central region of Krasnoyarsk, and had led or participated in more than 100 protests, including some in which he demonstrated alone.