Donald Trump's dealings with Russia have come under fresh scrutiny amid claims the US president concealed details of his conversations with President Vladimir Putin.
Mr. Trump came out fighting on Saturday night, dismissing as "insulting" an explosive report that claimed the FBI secretly launched an investigation into whether the president was working on behalf of Russia while in office.
Even as House Judiciary Committee Chairman Jerrold Nadler said his panel would look into the report, fresh claims emerged about a lack of transparency surrounding encounters with Mr Putin.
After a 2017 meeting with the Russian president in Hamburg, Mr. Trump took possession of the notes of his own interpreter and instructed the linguist not to discuss what had transpired with other administration officials, the Washington Post reported, citing current and former US officials said.
US officials discovered Mr. Trump’s actions when a White House adviser and a senior State Department official sought details about the meeting from the interpreter beyond a readout shared by Rex Tillerson, the then-Secretary of State, the newspaper reported.
In what would be considered unusual for any presidency, US officials reportedly said there was no detailed record, even in classified files, of the president's face-to-face interactions with the Russian leader on five different occasions.
In a telephone interview with Fox News host Jeanine Pirro on Saturday night, Mr. Trump said he did not take particular steps to conceal his private meetings with Mr Putin.
“Anyone could have listened to that meeting. That meeting is open for grabs,” he said, without elaborating.
Asked if is or has ever been working for Russia, Mr. Trump replied: "I think it's the most insulting thing I've ever been asked. I think it's the most insulting article I've ever had written, and if you read the article you'll see that they found absolutely nothing."
Mr. Trump went on to say that no president had taken a harder stance against Russia than he had.
"If you ask the folks in Russia, I've been tougher on Russia than anybody else, any other ... probably any other president, period, but certainly the last three or four presidents," he said.
The New York Times reported on Friday that the FBI launched the previously undisclosed counterintelligence investigation to determine whether Mr. Trump posed a national security threat, at the same time that it opened a criminal probe into possible obstruction of justice by the president.
The decision was said to have been taken after Mr. Trump fired James Comey, the FBI director leading the Russia election meddling investigation at the time, in May 2017.
The FBI investigation was subsequently folded into the broader probe by Special Counsel Robert Mueller, who is thought to be in the final stages of an investigation into Russia's meddling in the 2016 electionand possible collaboration by the Trump campaign.
No evidence has publicly emerged that Mr. Trump was secretly in contact with or took direction from Russian officials, the newspaper said.
The president had earlier hit out at the FBI on Twitter, saying the agency had "no reason" and "no proof" to launch such an investigation.
Mr. Nadler said such standard reactions from Mr. Trump "do nothing to address the incredibly serious nature of these allegations".
"There is no reason to doubt the seriousness or professionalism of the FBI," Mr Nadler said in a statement which said his committee "will take steps to better understand both the president's actions and the FBI's response to that behaviour, and to make certain that these career investigators are protected from President Trump's increasingly unhinged attacks."
Secretary of State Mike Pompeo, who was CIA director at the time the investigation was launched, declined to comment on The New York Times report, but insisted in an interview with CBS that "the notion that President Trump is a threat to American national security is absolutely ludicrous."
