The shock move comes days after Comey testified on Capitol Hill about the FBI's investigation into Russia's election meddling and a possible collusion between the country and Trump's campaign.
Comey states that Trump asked him on several occasions to publicly state that he was not under investigation.
He said it has now become clear that the ex-FBI chief was one of the leakers of 'privileged information' and should be investigated.
The White House previously said Trump only decided to oust Comey after meeting with Attorney General Jeff Sessions on Monday and Deputy Attorney General Rod Rosenstein, who discussed reasons for removing the director.
Trump had said he is ready to testify over Comey conversations.
"There should be no fuzz on this whatsoever. The Russians interfered in our election during the 2016 cycle," Comey said.
Comey confessed that he leaked the information about his interaction with the US president.
Trump's assertion came after he branded Comey as a "leaker".
"I just fired the head of the FBI. He was crazy, a real nut job," Trump told Lavrov, according to a media report.
The President has maintained that he has nothing to do with Russia.
Former Federal Bureau of Investigation director James Comey has said in a farewell letter to his colleagues in the agency that US President Donald Trump has the right to fire him for any reason, "or for no reason at all", a day after he was unceremoniously removed from his post.
'J'One of the reasons Jim Comey was fired was because he wouldn't pledge loyalty to Trump, which meant that whatever Trump is hiding would be dismissed or the investigations will be stopped.'
James Comey called for a national moment of reflection, in which everybody, regardless of partisan views, to evaluate the President and to consider whether he presents a threat to America itself.
Comey did not make any major new revelations about alleged links between Trump or his associates and Russia.
'Trump will do significant damage in the short term'
In "A Higher Loyalty: Truth, Lies, and Leadership", James Comey will "explore what good, ethical leadership looks like and how it drives sound decisions", according to Pan Macmillan, which has acquired the publishing rights in the United Kingdom and the Commonwealth excluding Canada.
Comey is scheduled to appear before the Senate Intelligence Committee on Thursday.
The FBI chief said that in the last presidential elections, the Russians were not able to change the actual vote tally, but one day they might.
'He is a good guy. I hope you can let this go,' Trump had said, adding that Flynn had done nothing wrong.
Clinton and her campaign pressed America's top cop, FBI Director James Comey, to put out the "full and complete facts" about a renewed probe into a cache of recently discovered emails, as the development emboldened Republican rival Donald Trump to seize on to the reignited controversy.
The Federal Bureau of Investigation Director James Comey said the money was worth it.
Wray is a litigation attorney with law firm King & Spalding in Washington and Atlanta.
The White House has said there is no evidence of a Trump-Russia collusion, hours after the Federal Bureau of Investigation confirmed that it was probing Russia's meddling in last year's presidential polls, including possible links between the Trump campaign and Moscow.
"San Bernardino involved two killers who were radicalised for quite a long time before their attack," FBI Director James Comey said.
The agency's director told lawmakers that it hasn't changed its opinion that Hillary Clinton should not face criminal charges after a review of new e-mails.
The FBI chief also trashed President Donald Trump's allegation that his Trump Tower was wiretapped on the orders of his predecessor Barack Obama.
In a big relief to Hillary Clinton, the Federal Bureau of Investigation on Tuesday ruled out charging the Democratic presidential candidate over allegations that she violated rules by using a private email server while she was United States Secretary of State.
Comey said from the investigations so far it is not entirely clear at this point just what terrorist group he aspired to support.
The 78th Annual Golden Globe awards have been announced. A quick look at the winners.
"I was on the way to winning until the combination of Jim Comey's (sic) letter on October 28th and Russian WikiLeaks raised doubts in the minds of people," she said.
Hillary Clinton has blamed the Federal Bureau of Investigation for her loss at the hands of her Republican challenger Donald Trump, claiming the decision to revive the probe into her email accounts stopped her momentum towards a historic win.
Wray, 50, received an overwhelmingly bipartisan support -- 92-5 votes -- on the Senate floor.
Bharara alleged that before firing him, Trump tried to cultivate relationship with him.
Investigators have also been looking for any evidence of possible financial crimes by Trump associates.
The Federal Bureau of Investigation has once again courted controversy as it released heavily redacted files from its 2001 investigation of President Bill Clinton's pardon of fugitive financier Marc Rich, just one week from election day.
The book 'Shattered: Inside Hillary Clinton's Doomed Campaign' reveals how in a flurry of calls the White House urged Clinton to concede defeat.
The FBI chief has warned that the Islamic State has become a bigger threat to the United States than the Al Qaeda as the dreaded group has influenced a significant number of Americans through social media and instructed them to carry out attacks in their own country.
The nominations for the Golden Globes have been announced.
Trump's apparent confirmation that he is under probe for obstruction of justice by special counsel appointed to probe alleged Russian meddling in the 2016 presidential polls came a day after a Washington Post report pointed to such an investigation.
A Democratic lawmaker has called for impeachment of United States President Donald Trump for his alleged involvement in obstruction of justice, after news reports revealed that he had asked the Federal Bureau of Investigation to stop investigations against former national security advisor Michael Flynn.