The European Union ad the United States on Saturday welcomed the unexpected release of prominent Belarus rights activist Ales Belyatsky, while urging the government to release other political prisoners as well.
A statement from the office of EU foreign policy chief Catherine Ashton said the freeing of Ales Belyatsky after three years was "an important step by the Belarusian authorities and should be followed without delay by the release of all the remaining political prisoners."
The statement appeared to hold out a possible review of EU sanctions should Minsk move to free others and restore their civic rights, saying "this could contribute to improving relations between the European Union and Belarus."
Washington also hailed what it called a "positive development", adding: "We reiterate our call for the government of Belarus to immediately and unconditionally release all the political prisoners who remain in detention and restore their political rights."
The EU last October renewed sanctions against the close ally of Russia, saying it had failed to make sufficient progress on human rights.
More than 200 people and 25 entities were left facing a freeze of their assets inside the EU and a travel ban.
Belarus arrested scores of people after a massive opposition protest on the night of the December 2010 presidential election.
Several candidates opposing re-elected Alexander Lukashenko, as well as other opposition leaders, were later sentenced to long jail terms.
Belyatsky said after his release from a high-security penal colony that he would continue to fight for rights.
The director of a human rights organisation called Vyasna (Spring), which helps victims of political repression under Lukashenko, he has won several top European awards and has been repeatedly nominated for a Nobel Peace Prize.
In November 2011, Belyatsky was jailed for four-and-a-half years on tax evasion charges on the grounds that Vyasna used bank accounts in Poland and Lithuania to collect donations for helping political prisoners, a criminal activity under Belarussian laws.
On Saturday political experts said Belyatsky's release might indicate that Lukashenko was concerned by Moscow's showdown with the fellow Slavic nation of Ukraine and was keen to mend fences with the European Union.