Amnesty International says the handing over contradicts Kazakhstan's obligations under international law because the eight are at risk of torture or other ill-treatment in their home country.
The London-based group says Ruhiddin Fahruddinov, Abdurahman Ibragimov, Tohir Abdusamatov, Sharofuddin Latipov, Nozim Rahmanov, Alisher Mirzaholov, Abdurauf Holmuratov, and Alizhon Mirganiev were returned to Uzbekistan on 29 November.
According to reports, only two of them have been given access to lawyers.
Four of the eight are allegedly wanted by the Uzbek authorities for "participation in a banned religious organization." Two others are wanted for "attempting to overthrow the constitutional order." The reason for the arrest of the other two men is not known.
Amnesty says it is unaware of whether any of the eight men have been charged to date.
(Amnesty International press release)
Workers at Almaty polling station No. 310 registering election monitors prior to the opening of voting on December 4