In another tweet this week, Mr. Trump had said: "After 7 months of investigations & committee hearings about my 'collusion with the Russians, ' nobody has been able to show any proof. Witch Hunt", Trump tweeted on Friday morning. It comes a day after a new report indicated that he is under investigation for obstruction of justice.
Comey told Congress last week he believes he was sacked by Trump to undermine the agency's Russian Federation probe.
US President Trump had received private assurances from sacked Federal Bureau of Investigation Director James Comey that he was not being personally investigated for alleged Russian interference into the US election.More news: Syrian President Assad may be readying 'potential' chemical attack
The scoop is from the Washington Post, who cite five anonymous sources.
Trump was forced to fire Flynn in February after he misled the White House about his contacts with Russian officials a year ago as a member of Trump's transition team.
The second, the source continued, is whether any potential offences were committed, Mr Trump or others attempted to cover them up or obstruct the investigation into them.
Robert S. Mueller III is the special counsel leading the obstruction of justice case, and has asked for interviews with three senior intelligence officials in an effort to get their sides of the story.
While a sitting president is unlikely to face criminal prosecution, obstruction of justice could form the basis for impeachment.
"We may have our differences, but we do well in times like these to remember that everyone who serves in our nation's capital is here because above all they love our country", Trump said at the White House.