In a statement on December 1, the New York-based rights group called on the international community -- in particular the European Union and the United States -- to continue to press Uzbek officials to free political prisoners.
Holly Cartner, HRW's director for Europe and Central Asia, said HRW was happy about the release of Umarov, "who should have never been imprisoned in the first place."
Umarov, a prominent businessman, founded the opposition Sunshine Uzbekistan Coalition early in 2005. He was arrested later that year on embezzlement and tax-evasion charges and in 2006 a court sentenced him to 14 years in jail.
Umarov has denied any wrongdoing.
On November 15, after serving four years of a seven-year prison sentence, Umarov was released under a government amnesty. HRW said that on November 21 Umarov was reunited with his wife and children in the United States.
The group said Umarov was released in poor health and has not yet been acquitted of the charges against him, which HRW said are politically motivated.