Cambodia's U.N.-backed war crimes tribunal says it has begun contempt proceedings against VOA's Khmer service for disclosing confidential documents about the prosecution of Khmer Rouge defendants with suspected links to genocide in the 1970s.

The tribunal's move drew an immediate statement of concern Thursday from VOA administrators, who said the probe is unwarranted and could have a chilling effect on coverage of an important international news story. It also said VOA and its Khmer service are committed to providing objective, comprehensive coverage of proceedings before the tribunal.

The contempt case stems from a series of interviews last month in which VOA Khmer mentioned three mid-level Khmer Rouge suspects who had been named by court prosecutors in confidential court papers. The suspects had already been identified by name by the Christian Science Monitor (newspaper) and a New Zealand Web site in June. VOA video reports during August included images of the original court documents.

The move against the U.S.-funded broadcaster marks the first time the tribunal has followed through on warnings to launch contempt proceedings. No timetable for legal action has been announced.

In its landmark first trial, the tribunal last year sentenced former Khmer Rouge lieutenant Kaing Guek Eav, better known as Duch, to 30 years in prison for his role as chief of the notorious Tuol Sleng torture prison during the Khmer Rouge's 1975-1979 reign.

The tribunal later reduced the sentence to 19 years, granting Duch credit for time served. Duch has appealed the guilty verdict, and the tribunal said Thursday it hopes to rule by the end of this year whether the conviction should be overturned.

The four most senior surviving members of the former Khmer Rouge, including nominal head of state 79-year-old Khieu Samphan, are set to face trial in the coming months. They face charges of religious persecution, torture and genocide in the deaths of as many as 2 million people.

Khmer Rouge leader Pol Pot died in 1998.