The four activists -- Saida Kurbanova, Ma'mur Azimov, Ziyodulla Razakov, and Uktam Pardaev -- had traveled to the capital, Tashkent, from Jizakh on September 17 at the invitation of the Free Peasants opposition party to discuss the country's economic situation.
They were detained at a Tashkent hotel the next day and interrogated. Police say they were acting on a telephone call alerting them to suspicious people in the hotel.
The four were released after four hours in detention.
Uzbek right groups consider the incident an attempt to intimidate their regional colleagues.
The incident happened the same week that Uzbekistan's Foreign Minister Vladimir Norov was in Brussels to discuss a European Union visa ban and arms embargo against Tashkent. EU sources told RFE/RL that Norov railed against the sanctions, calling them an example of "double standards."
Jean-Pierre Jouyet, the French secretary of state for European affairs, who represented the EU at the meeting, said he had visited Tashkent in July and saw "progress."
(by Sojida Djakhfarova, director of RFE/RL's Uzbek Service)