US President Donald Trump is under investigation for possible obstruction of justice by Robert Mueller, the special counsel examining Russias interference in the 2016 election, a media report said.
In response, Trump on Thursday mocked federal investigators for making up a "phoney collusion with the Russians story", the New York Times reported.
"They made up a phoney collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phony story.
Nice, " Trump tweeted.
In a later tweet, the President once again called the Russia investigation a "witch hunt" and called the people leading it "very bad", apparently a reference to Mueller and others at the Federal Bureau of Investigation.
Mueller has requested interviews with three current or former senior intelligence officials, the Washington Post reported on Wednesday.
The move suggested Mueller is examining whether Trump sought their help in trying to get former FBI chief James Comey to end an investigation into Michael T. Flynn, the former National Security Adviser.
The special counsel is also seeking documents from the National Security Agency relating to its interactions with the White House on the Russia connection investigation.
The requests from Mueller also pointed towards a new scrutiny on whether the President tried to influence the Russia investigation through conversations he had with Comey, whom he ultimately fired, or with other officials.
That would make Trump a subject of a sprawling inquiry that he repeatedly said has no merit.
Director of National Intelligence Daniel Coats, National Security Agency's head Mike Rogers, and Rogers's recently departed deputy Richard Ledgett agreed to be interviewed by Mueller's investigators as early as this week, the Post reported.
It is unclear how many others have been questioned by the FBI, the sources told the daily.
Investigators were also looking for any evidence of possible financial crimes among Trump associates.
The NSA said in a statement that it will "fully cooperate with the special counsel" and declined to comment further.
In response to the report, Mark Corallo, a spokesman for Trump's personal attorney Marc Kasowitz, said: "The FBI leak of information regarding the President is outrageous, inexcusable and illegal. "
Comey testified last week before the Senate Intelligence Committee, where he gave a detailed account of his conversations with the President, who he said asked him for his "loyalty" and insinuated that his job as FBI chief might depend on providing such a pledge.
Mueller, who headed the FBI for 12 years and was Comey's predecessor in the post, has the confidence of both Democratic and Republican lawmakers.
The crime of obstruction of justice could lead to a move to impeach Trump in Congress, something that some Democratic lawmakers had called for, provided that the unfolding facts prove that to be warranted.