"Hundreds of people (who are Hizbu Tahrir members) are victims of investigations, interrogations and persecution in Russia, without knowing what they are guilty of," Valentin Ponomaryev of the Memorial human rights group told a press conference on Wednesday.
Ponomaryev accused the FSB secret services of conducting a "disinformation" campaign against Hizbu Tahrir, which calls for the establishment of an Islamic state and the creation of an Islamic Caliphate, or government, in the former Soviet states of Central Asia.
The latest example of the harassment is the 13 February arrest of Yusuf Kassimakhunov, a Hizbu Tahrir member suspected of "terrorist" activities, Ponomaryev said.
"His lawyer and family have not been able until now to find out where he is and had not received any legal aid," said Valentin Gufter, director of the Human Rights Institute.
Ponomaryev said that the February 2003 classification of Hizbu Tahrir as a "terrorist" organisation by Russia's Supreme Court was "a concession to Uzbekistan, which can now pursue its citizens (who are members of the party) on Russian territory and demand their extradition," Ponomaryev said.
"His (Yusuf Kassimakhunov's) lawyer and family have not been able until now to find out where he is and had not received any legal aid"
Director, Human Rights Institute
Uzbekistan accused the group of trying to overthrow the regime.
Rights groups say more than 4000 Hizbu Tahrir adherents are in Uzbek prisons serving sentences of up to 20 years.
The Hizbu Tahrir, a movement founded in the Middle East in the 1950s, established itself in Central Asia 10 years ago, at first in the Ferghana valley in Uzbekistan, and then in neighbouring Tajikistan and Kyrgyzstan in the late 1990s.