Uzbeks, arrested in Russia on suspicion of taking part in an uprising, have been tortured, the Russian human rights group, Memorial, said on Friday.
According to the group, 14 people of Uzbek origin - 12 Uzbek nationals, a Russian and a Kyrgyz - were detained at Ivanovo, northeast of Moscow, in June following a request by the authorities in Tashkent.
The arrests were linked to the insurrection in the eastern Uzbek town of Andijan last May.
Tashkent says 187 people were killed in the uprising, but non-governmental organisations (NGOs) put the figure at between 500 and 1000.
Memorial says the 14 were beaten and given electric shocks in the presence of Uzbek interrogators, who threatened to "get even" with the detainees if they were sent home.
The detained men deny links to the Andijan uprising and membership in the Akromiya movement, accused of organising the uprising, according to Russian NGOs.
A second Russian NGO, Civil Contribution, has written to the Russian Prosecutor General, Vladimir Ustinov, asking him to look into the torture charges as a matter of urgency.
The Uzbek request for extradition is under consideration by the prosecutor's office, and Civil Contribution fears the 14 may be sent back at any moment.
Russia backed Tashkent's crackdown of the Andijan uprising.