Amnesty International says an Uzbek man who disappeared after being released from a Russian prison was abducted and forcibly returned to Uzbekistan to face trial there.
Azamat Ermakov was arrested in Russia in 2009 following an extradition request from Uzbekistan, where he had been accused of involvement with religious extremists.
The European Court of Human Rights attempted to block his extradition, but Ermakov disappeared within hours of his release from a Nizhny Novgorod prison in November 2012.
In a statement, Amnesty cites evidence that Ermakov is now being held in pretrial detention in the Uzbek city of Andijon and faces a "real risk" of torture and ill-treatment.
Rights groups say as many as 10 Central Asians have been illegally extradited from Russia in the past year to face trial and likely abuse in their home countries.