"This is very bad news," Zernova said. "The case was handled by Russia's human rights organization Memorial and, as far as we know, the acquittal verdict should have remained in force."
There was no immediate confirmation from Russian authorities.
A jury in Russia's Tatarstan Republic in September acquitted former Guantanamo Bay detainees Timur Ishmuratov and Ravil Gumarov of charges of involvement in the explosion of a gas pipeline in the town of Bugulma in January 2005. Another suspect in the case, Fanis Shaikhutdinov, was also acquitted.
Ishmuratov and Gumarov are among seven Russian citizens who were captured in Afghanistan and subsequently released from Guantanamo Bay in 2004 for lack of evidence and returned to Russia.
Another former Guantanamo inmate, Rasul Kudayev, was detained in Russia's southern republic of Kabardino-Balkaria after last October's militant raid on the regional capital, Nalchik. Kudayev has denied any involvement in the attack.
2005 In Pictures
A slideshow of images related to the top news stories of 2005.