Azerbaijan police raided the Baku bureau of U.S.-government-funded Radio Free Europe early Friday, shutting down the office and ordering its journalists to stop working.
RFE chief editor Nenad Pejic called the raid "a flagrant violation of every international commitment and standard Azerbaijan has pledged to uphold."
He told VOA that officials from the state prosecutor's office took documents and questioned staff members from Radio Azadliq into Friday evening.
The broadcaster has received no details on why it was targeted. "No allegations," Pejic said. "What we do know is they say they (are investigating) our operations. That's it."
"We assume (staff) are going to be asked questions about our operations, maybe about salaries, maybe who works, who doesn't work — this kind of stuff," he added. "Frankly, this is, from my point of view, not important at all, because officials are going to say what they want to say."
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Pejic said the action was unsurprising for a government that has demonstrated increasing hostility toward the media, with at least 200 journalists arrested annually for the past three years.
Jeff Shell, chairman of the U.S. Broadcasting Board of Governors, which funds RFE/RL, called on the Azeri government to allow the bureau to immediately reopen.
"This unwarranted action is an escalation of the Azeri government's abusive attempt to intimidate independent journalists and repress free media," Shell said.
A U.S. State Department senior official said the U.S. is "deeply disturbed" by reports that employees of the RFE/RL bureau in Baku have been detained in their offices and questioned while the premises were searched by police.
The State Department official called on "responsible authorities" to respect Azerbaijan's "international commitment to protecting media freedom," saying a free and independent press is "critical to the well-being of the nation."
Earlier this month, an Azeri court ordered RFE journalist Khadija Ismayilova held in pre-trial detention for two months over allegations she attempted to pressure a man to commit suicide. A petition for her release was denied Friday as the raid was happening.
Shell also requested Ismayilova's release.
Pejic said the staff in Baku was continuing to work from private apartments. He expected only a minor impact on programming, with journalists in Prague updating online and TV operations.
In a 60-page statement in early December, Azeri Chief of Staff Ramiz Mehdiyev singled out the RFE bureau and likened its work to "treason."
"Overall, there is an understanding within the society that Radio Azadliq and its employees are on a disgusting path," Mehdiyev said. "There is no need to prove that provision of false information is the same as working for the foreign secret service. This is treason.
"If the symbol of democracy is Khadija Ismayilova, then it is awful to imagine what future awaits the society."
Arzu Geybullayeva, an academic fellow with RFE/RL who works with the Azerbaijan staff from Prague and monitors press freedom issues in her native country, said the raid was expected, though staff had no warning of when it would come.
Azerbaijan, she said, has been in a "downward spiral" with regard to media. Press watchdog Reporters Without Borders ranked the country 160th out of 180 in its press freedom index this year, four points below its 2013 score.
"Once the chief of staff went on against the radio, accusing it of treason and of spreading lies, it was clear that something was going to happen," Geybullayeva said. "And Khadija's arrest was, I guess, the beginning of what was to come."
U.S. officials have called for Ismayilova's release, saying the case was the latest attempt by the Azeri government to silence its critics and restrict press freedom.
Pejic said the charges against Ismayilova were part of "a two-year campaign to silence a journalist who has investigated government corruption and human rights abuses in Azerbaijan."
Ismayilova has reported extensively about the business dealings involving relatives of Azerbaijan's president, Ilham Aliyev.
Geybullayeva said the RFE bureau's closure marked the end of one of the remaining sources of independent local reporting for Azerbaijan. She said she doubted the bureau, like other news services that government officials cut off before it, would reopen its doors.
"This is the last blow to the independent opinions in Azerbaijan, given the direction Azerbaijan is headed," Geybullayeva said. "I'm afraid to say that I don't think there's anyone left."
RFE/RL is funded through grants from the U.S. Broadcasting Board of Governors, which also oversees VOA. RFE/RL's Azerbaijani Service was established in 1953.