His claims come as Attorney General William P. Barr has taken steps to review the origins of the Russia probe, including the appointment of a senior prosecutor to examine the roles of the FBI and the CIA.

Trump has long claimed that his campaign was subject to illegal surveillance and has used the term “spying” to characterize what he says took place. In recent congressional testimony, Barr said “spying” did occur, but he has not said the surveillance was unjustified.

At a Senate hearing earlier this month, FBI Director Christopher A. Wray — also a Trump appointee — said he had not seen any evidence that illegal surveillance was conducted on individuals associated with Trump’s campaign. He also said “spying” was not a term he would use. Trump subsequently called Wray’s testimony “ridiculous.”

In an interview broadcast Friday on Fox News, Barr, who took office in February, said many questions about the origins of the probe remain unanswered.

“I’ve been trying to get answers to questions, and I’ve found that a lot of the answers have been inadequate, and I’ve also found that some of the explanations I’ve gotten don’t hang together,” he said. “In a sense, I have more questions today than when I first started.”

Trump has stepped up his calls to investigate the investigators of Russian election interference in the wake of the release of the report of special counsel Robert S. Mueller III.

Mueller’s report concluded that the Russian government interfered in the 2016 presidential election “in sweeping and systematic fashion.”

The interference included both a social media campaign that favored Trump and disparaged Democrat Hillary Clinton, and the hacking of computers maintained by allies of Clinton and the subsequent releases of stolen documents.

The report did not find sufficient evidence to bring charges of criminal conspiracy with Russia against Trump or anyone associated with his campaign. It did not offer a conclusion on whether Trump obstructed justice.

Barr later concluded that there was not sufficient evidence for obstruction of justice, but House Democrats are continuing to pursue that issue.

Republicans have accused FBI leaders of using flimsy or false claims to get court surveillance orders on former Trump adviser Carter Page in 2016 and 2017. They have also accused senior FBI officials of political bias against Trump. Current and former FBI officials have defended the bureau’s actions, saying they were obligated to investigate allegations of wrongdoing.

In his tweets, Trump cited a Fox News poll released Thursday that found that 58 percent of voters think it is “at least somewhat likely the FBI broke the law” when it first started investigating the Trump campaign.

Trump overstated the finding, writing that “58% of people say that the FBI broke the law in investigating Donald J. Trump.”

Trump has long expressed ire toward former FBI director James B. Comey, whom he fired amid the Russia probe in 2017.

In another tweet on Friday, Trump wrote, “What happened is that Donald Trump won. Down goes Comey.” He attributed the quote to Fox News’s morning program “Fox & Friends.”