Felix Corley, Forum 18's editor, said from London on Wednesday that the situation had been bad since 1998 - when Uzbekistan's religious laws were changed - but it had got "far worse" in the past year.
Forum 18 is a Norwegian-based organisation that promotes the implementation of Article 18 of the Universal Declaration of Human Rights and concentrates on serious religious freedom.
It said heavy increases in penalties on unregistered religious activity were introduced last December in the Central Asian state.
Administrative and criminal codes were also changed in June, severely increasing penalties for the unapproved publication of religious literature.
Corley said the censorship of religious literature had been stepped up.
"At the same time, we've got very severe raids on religious communities, detentions of religious believers, beatings and the deportation of foreigners who have been involved in religious activities in Uzbekistan," Corley said. "This is something new that has been stepped up in the last couple of months.”
Igor Rotar, an activist with Forum 18, reported on Tuesday that Uzbek authorities had withdrawn the registration of a Jehovah's Witness community in the eastern city of Ferghana. The country had one remaining Jehovah's community that was registered.
Rotar's report said that were it not for official discrimination, the Jehovah's Witnesses could have registered "dozens" of congregations in the former Soviet republic.
Forum 18 said Tashkent planned to introduce even harsher penalties. They would, if adopted, mean people trying to spread their faith would be heavily punished, Corley said.
The government had closed foreign NGOs it believed were involved or linked to religious activity.
Corley said the country's Muslim community was "more tightly controlled" than any faith, with the government telling imams what they could preach and, in reality, appointing them as well.
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