WASHINGTON -- In the eyes of U.S. investigators, American journalist Andrew Feinberg was on the inside of the Russia propaganda machine. FBI agents interviewed Feinberg for two hours on September 1 about his former employer, the Russian web-based media outlet Sputnik.

"What did they want to know?" asked CBS News national security correspondent Jeff Pegues.

"They wanted to know how I ended up there, you know, who paid me, who signed my checks, what a typical day was like," Feinberg said. "Who I took my orders from … they wanted to know everything."

Andrew Feinberg CBS News

According to a declassified report issued in January, U.S. intelligence analysts concluded Sputnik was part of the massive Russian intelligence campaign to spread misinformation during the 2016 election.

Investigators believe there was a combination of "covert intelligence operations," "paid social media trolls" and "state-funded media," all of which is now under investigation by special counsel Robert Mueller.

Sputnik did not respond to numerous requests for comment but recently told Yahoo News it was "a news organization dedicated to accurate news reporting."

"Is it Russian propaganda?" Pegues asked.

"Yes," Feinberg said.

Feinberg took the job believing he would be allowed to report freely, but after four months he was fired. He said he was fired for refusing to do a story he thought was wrong. Sputnik alleges it was over his performance, but Feinberg said he has proof of meddling by Moscow in the 6,000 emails handed over to the FBI.

"They only will run a story ... when it meets a certain criteria that the angle that the story takes is one that meets their worldview," he said.

"The worldview of Vladimir Putin?" Pegues asked.

"Well that's where the money's coming from," Feinberg said.

Feinberg said the U.S. has opened itself up to a "kind of hybrid warfare, this kind of information warfare, because we allow them to use the First Amendment and our country's commitment to a free press against us because we're very reluctant to go to an organization like Sputnik that's operating as a news agency and say, 'Well you're not really a news agency, you're propaganda.'"

The FBI would not comment.

Meanwhile, the Justice Department recently asked another Russian-owned media organization, RT America, to register as a foreign agency. RT told CBS News that any claims it engages in political activity are "entirely baseless."