One month before the end of his four-year sentence, Jehovah's Witness Abdubannob Ahmedov received an additional 30-month sentence on charges of violating prison rules.
Two other Jehovah's Witness prisoners of conscience also had their prison terms extended, but have now been freed.
Four Muslims were also freed, on condition of speaking publicly in favour of government policies.
Overall, Uzbek authorities continue their crackdown against religious believers and their activities, focusing on Protestants, Muslims and Jehovah's Witnesses without distinction.
Abdubannob Ahmedov, from Fergana (central Uzbekistan), was given a new prison sentence of two and a half years. The sentence came just a month before he was due to complete a four-year prison term on 23 July, Forum 18 News Service reported.
Four years earlier, he was convicted on alleged "illegal religious activities". He was convicted again in accordance with Article 221 of the Criminal Code for violating prison rules.
The fate of Yelena Kim, a Baptist also from Fergana, remains a mystery. She faces up to three years' imprisonment on charges of "illegally teaching religion".
Police raided her home in late June, seizing various documents, including books, videos, Bibles, hymns as well as personal papers.
Uzbek authorities deny that religious freedom is violated in their country. However, each community has to apply for a state permit to exercise it.
And the former are fickle about issuing such permits.
Protestants, Catholics, Muslims and Jehovah's Witnesses are among the most affected groups with some of their members brought to trial and convicted.