Attorney General William Barr is not backing down from claims that he believes unauthorized spying took place on President Trump's campaign during the 2016 presidential election as the Justice Department makes moves to investigate the origins of the Russia probe. FBI officials have denied that the agency spied on the president's campaign.

In two separate interviews, Barr doubled down on his assertion that illegal spying did take place, a claim he made before senators last month. In a conversation with Fox News' Bill Hemmer on "America's Newsroom," Barr suggested that he wanted to get to the bottom of whether "government officials abused their power and put their thumb on the scale" during the Russia investigation. He criticized unnamed officials as providing "inadequate" explanations for what took place.

"People have to find out what the government was doing during that period," said Barr, adding that if the U.S. government is concerned about foreign influence in the U.S. election process, it should be equally worried about potential abuses of power within the federal government. Barr said he wouldn't "speculate" on when such alleged spying exactly started.

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In a separate interview with the Wall Street Journal, Barr appeared more certain, asserting, "Government power was used to spy on American citizens."

"I can't imagine any world where we wouldn't take a look and make sure that was done properly," he added.

Barr had previously told lawmakers that he was assembling a team at the Justice Department to "review the conduct of the investigation" and wanted to "try to get my arms around all the aspects of the counterintelligence investigation that was conducted during the summer of 2016." That investigation into the origins of the Russia probe is separate from the long-running Office of Inspector General investigation into the Justice Department's handling of the Russia investigation.

Barr told Fox that the initial Russia probe was handled on an "ad hoc approach" by many DOJ and FBI officials that have since left the federal government.

"I think there's a misconception out there that we know a lot about what happened. The fact of the matter is Bob Mueller did not look at the government's activities. He was looking at whether or not the Trump campaign had conspired with the Russians. But he was not going back and looking at the counterintelligence program. And we have a number of investigations underway that touch upon it," Barr said.

The attorney general's assertion of spying, however, has been twice denied by current and former FBI officials. When asked directly about Barr's claims before Congress, FBI Director Christopher Wray testified to the Senate Appropriations Committee that he wasn't aware of any illegal "spying" on the Trump campaign in 2016.

"That's not the term I would use," Wray said when asked if the word "spying" describes what the FBI does when it investigates alleged mobsters or terrorists.

Former FBI Director James Comey also maintained that he had "no idea" what Barr was talking about when he brought up the claim of unauthorized spying.

"The FBI doesn't spy, the FBI investigates," Comey said on "CBS This Morning". "We investigated a very serious allegation that Americans might be hooked up with the Russian effort to attack our democracy."

Barr's claims fall in line with Mr. Trump's repeated assertion that spying took place on his campaign, something he suggested amounts to "treason."