"Nice", Trump wrote on Twitter.
Mr Comey, who was sacked on May 9, told the Senate Intelligence Committee last week he believed President Trump dismissed him to undermine the FBI's Russian Federation probe.
Comey said it should be special counsel Robert Mueller's task to determine whether Trump had obstructed justice, and therefore, had opened himself up to possible impeachment proceedings, keeping the allegations on Russian Federation in mind.
Trump fired FBI Director James Comey in May, and that firing is now reportedly part of an investigation into whether Trump obstructed justice as president.
Significantly, Preet Bharara, the India-born former top United States federal prosecutor, earlier this week had said that there was enough evidence to begin an obstruction of justice case against Trump over his alleged interference in the Russian Federation probe.
Recently, Comey made a startling revelation, accusing the White House of "lies".
Comey prepared multiple contemporaneous memos documenting conversations with Trump that made him uneasy in the weeks before his May 9 firing. "Sad!" the U.S. president tweeted.
Mr Trump, who is due to give a speech in Miami on Friday where he is expected to announce a shift in USA policy towards Cuba, also boasted about his deployment of social media, despite warnings by legal experts that his tweets may be used against him in the ongoing investigation.
E. coli bacteria found in drinking water at US Open
Day had two triple bogeys in the same round for the first time in his career and needed birdie on the par-5 18th to break 80. The good news came late on a day of mixed fortunes for the Australians on day one of the 117th US Open at Erin Hills .
Mueller is leading the Russian probe after being appointed by Deputy Attorney General Rod Rosenstein in the Department of Justice, which oversees the Federal Bureau of Investigation.
Mr Trump's legal team said the latest leak to the media was "outrageous".
Since appointed as special counsel last month, Mueller has not publicly discussed his work.
The Twitter attacks came as vice president Mike Pence hired a personal lawyer to represent him in the intensifying investigation. Comey also testified he had told Trump he was not under investigation.
The letter said the investigation will also probe Comey's testimony that Loretta Lynch, as President Barack Obama's attorney general, had directed him to describe an FBI probe into Hillary Clinton's email practices as merely a "matter" and to avoid calling it an investigation.
Several investigations could pose trouble for Trump.
Rep. Adam Schiff, the top Democrat on the House Intelligence committee, said such a move would "be the last straw" for many in Congress and would have "echoes of Watergate", when President Richard Nixon dismissed special prosecutor Archibald Cox over Cox's subpoenas for White House tapes.
Comments