The FBI is investigating whether the Russian news agency Sputnik is acting as a propaganda arm of the Kremlin, Yahoo News reported on Monday.

In response, a Kremlin spokesperson said the move smacked of censorship.

The bureau recently quizzed the Russian agency's former White House correspondent, Andrew Feinberg, over concerns that Sputnik is violating the Foreign Agents Registration Act (FARA) – which says foreign groups trying to influence U.S. public opinion must inform the Justice Department about their funding and operations.

The law was introduced in the United States in 1938, just before the outbreak of World War II in Europe, as a way of countering Nazi propaganda.

Open gallery view The Federal Bureau of Investigation headquarters in Washington, May 2017. Credit: Andrew Harrer/Bloomberg

Kremlin spokesman Dmitry Peskov was quoted on Sputnik as saying that "interrogations of journalists or ex-journalists in connection with journalistic activities certainly do not speak in favor of pluralism of opinion and freedom of the press. They rather speak about serious problems with censorship and limiting the work of the press."

Sputnik recently received accreditation to cover White House press briefings.

Yahoo News revealed Monday that the FBI received a "thumb drive containing thousands of internal Sputnik emails and documents" from Feinberg, "who had downloaded the material onto his laptop before he was fired in May."

Feinberg told Yahoo News that the FBI interview was focused on Sputnik’s “internal structure, editorial processes and funding.

“They wanted to know where did my orders come from and if I ever got any direction from Moscow,” he told Yahoo News. “They were interested in examples of how I was steered toward covering certain issues.”

It is unknown whether the FBI investigation is connected to the wider probe being led by former FBI Director Robert Mueller into potential Russian interference in the 2016 U.S. presidential election.

Asha Rangappa, a former FBI counterintelligence agent and now associate dean of Yale Law School, told Yahoo News the bureau’s questioning of Feinberg was “incredibly significant.

“The FBI has since the 1970s taken pains not to be perceived in any way as infringing on First Amendment activity," he said. "But this tells me they have good information and intelligence that these organizations have been acting on behalf of the Kremlin, and that there’s a direct line between them that are a significant threat to our democracy.”

Sputnik is owned by Rossiya Segodnya, which Yahoo News described as "a Russian government media operation headed by Dmitri Kiselyov, a broadcaster who is known as Putin’s 'personal propagandist.'"

Sputnik's U.S. editor in chief, Mindia Gavasheli, told Yahoo News: “Any assertion that we are not a news organization is simply false.”

He also said he was unaware of any FBI probe. “This is the first time I’m hearing about it and I don’t think anyone at Sputnik was contacted, so thank you for letting us know,” said Gavasheli.

The editor in chief believes the FBI's investigation is part of "the atmosphere of hysteria we are witnessing now. Anything being related to Russia right now is being considered a spycraft of some sort,” he told Yahoo News.

Yahoo News also reported that the FBI's questioning of Feinberg took place two weeks after a Yahoo interview in which Feinberg claimed he was fired as Sputnik's Washington bureau chief in May because he refused to ask a question about a now-debunked Fox News report at a White House press briefing.

Feinberg wrote an article about his experience at Sputnik for Politico in August, titled "My Life at a Russian Propaganda Network." In it he wrote: "Sputnik’s mission statement – 'Telling the Untold' – means that Sputnik’s content should reflect the Russian side of any news story, whether it lines up with reality or not."

In a separate development on Monday, Newsweek reported that workers associated with the U.S. arm of Russian news network RT (formerly Russia Today) have been asked to register as foreign agents.

Newsweek wrote that a company associated with RT America received a letter from the Justice Department saying that “the company is obligated to register” under the Foreign Agents Registration Act.

Newsweek quoted RT's editor in chief, Margarita Simonyan, as saying on the RT website: “The war the U.S. establishment wages with our journalists is dedicated to all the starry-eyed idealists who still believe in freedom of speech. Those who invented it, have buried it.”