Ramazan Yesergepov's jailing is the latest in a string of what activists say are rights infringements by Kazakhstan as it prepares to assume the chairmanship of a trans-Atlantic rights organization.
Yesergepov was arrested by security services officers in January after publishing correspondence in the small-circulation weekly Alma-Ata Info that appeared to show collusion in corruption between a Kazakh businessman and the National Security Committee, the successor agency to the KGB.
"Yesergepov was simply carrying out his professional duties in revealing socially important information to the general public," Rozlana Taukina, head of the Reporters in Danger advocacy group, said at a press conference Tuesday.
Media rights monitoring group Adil Soz said the case was politically motivated and aimed at intimidating journalists.
"The law has been broken in the crudest fashion, because the sentence was issued in a closed session, which is in breach of the International Covenant on Civil and Political Rights," Taukina said.
Kazakhstan ratified the covenant in 2005 as part of efforts to improve its democratic credentials among Western nations.
The case has also drawn sharp criticism from Paris-based Reporters Without Borders.
Yesergepov "had to defend himself during the trial, although the Kazakh constitution gives everyone the right to be defended by the lawyer of their choice," the group said in a statement.
Reporters Without Borders ranked Kazakhstan last year 125th out 173 countries in its press freedom index.
The National Security Committee could not be reached for comment.
In bidding for the 2010 chairmanship of the Organization for Security and Cooperation in Europe, Kazakhstan committed to a range of democratic reforms, including improving press liberties.
But opposition politicians and activists say the government continues to pressure independent media.
In a move condemned by the Organization for Security and Cooperation in Europe, President Nursultan Nazarbayev approved legislation last month that would subject Internet outlets - such as chat rooms, blogs and online stores - to the same criminal prosecution applied to traditional media.
Authorities say the legislation aims to curb the distribution of child pornography, extremist literature and other unsuitable material.
Opponents say the new rules will restrict criticism of the government.
Government critics accuse Nazarbayev of quashing political opposition and seeking to limit the dissemination of information. He has ruled the oil-rich Central Asian nation of 15 million - a former Soviet republic - since the collapse of the Soviet Union in 1991.
By: Kazakh rights activists denounced authorities Tuesday for sentencing a newspaper editor to three years in jail for gathering and divulging state secrets.