U.S. President Donald Trump has fired FBI Director James Comey, the top U.S. law enforcement official and the man who led the agency charged with investigating his campaign's ties with Russia.
As his reason for the May 9 dismissal, Trump cited what he said was Comey's mishandling of an investigation into Democratic presidential candidate Hillary Clinton's e-mails last year, saying both Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein had recommended Comey's ouster over that matter.
Trump told Comey in a letter that "while I greatly appreciate you informing me, on three separate occasions, that I am not under investigation [in connection with the Russia probe], I nevertheless concur with the judgment of the Department of Justice that you are not able to effectively lead the bureau."
"It is essential that we find new leadership for the FBI that restores public trust and confidence in its vital law enforcement mission," he said.
Trump defended Comey's firing in a series of tweets on May 10. Trump said Comey "will be replaced by someone who will do a far better job, bringing back the spirit and prestige of the FBI."
"Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike. When things calm down, they will be thanking me," Trump added on Twitter.
Democrats have criticized Comey for announcing a new twist in the Clinton e-mail investigation only days before the November 8 election -- a move Clinton said turned undecided voters against her at a crucial moment. But Democrats in Congress nearly unanimously denounced the president's decision to fire Comey.
The move shocked many in Washington and led to accusations from Democrats and others that the White House was trying to undermine the FBI probe involving Russia.
WATCH: Senate Democratic Leader Blasts Comey Firing
Senator Ben Cardin of Maryland, the top Democrat on the Senate Foreign Relations Committee, said Trump's dismissal of Comey was "beyond the pale – even for him."
"This is the biggest evidence to date of why we need an independent commission to investigate Russia’s interference in our election," Cardin said in a statement. "We also need a special prosecutor to complete the ongoing criminal probe, now that the president has undermined the integrity of the FBI’s investigation."
LISTEN: White House Press Secretary Sean Spicer defends the dismissal of FBI Director James Comey. This is an audio recording of a press gaggle with Spicer in Washington on May 9. (Reuters)
In January, the U.S. intelligence community issued an assessment charging that Russian President Vladimir Putin ordered an "influence campaign" seeking to undermine faith in the U.S. electoral system and denigrate Democratic candidate Clinton. It said that Russia developed a clear preference for Trump.
With Comey having testified only days ago about about the FBI's ongoing investigation into Russia's suspected efforts to help Trump get elected, Senator Patrick Leahy (Democrat-Vermont) said the firing brings back memories of President Richard Nixon's firing of a special prosecutor investigating the Watergate scandal in a famed "Saturday night massacre" in 1973.
"It's nothing less than Nixonian," Leahy said.
Democrats: 'Big Mistake'
Senate Democratic leader Charles Schumer of New York said he told Trump it was a "big mistake" to fire Comey.
"We know the FBI has been looking whether the Trump campaign colluded with the Russians, a very serious offense. Were these investigations getting too close to home for the president?" Schumer asked.
Schumer called on Rosenstein to make good on his promise in testimony before Congress that he would appoint a special prosecutor to investigate Russian meddling in the election, if necessary, to ensure the White House did not interfere with the probe.
"This investigation must be run as far away as possible from this White House, and as far away as possible from anyone that President Trump has appointed," Schumer said.
Senator Richard Durbin of Illinois, the second-ranking Democrat in the Senate, said any attempt by Trump to undermine the Russia investigation through Comey's dismissal "would raise grave constitutional issues."
Durbin called on the White House to immediately say whether the administration intends to continue the Russian investigation under a new FBI director.
Most Democrats backed Schumer's call for a special prosecutor to investigate the allegations of Russian election meddling, saying the White House cannot be trusted to appoint someone who will retain such independence.
At least one prominent Republican -- Senate Armed Service Committee Chairman John McCain of Arizona -- agreed that a "special committee" is needed to take over the Russia investigation.
But other Republicans in Congress appeared more supportive of Trump's decision, with Senate Majority Leader Mitch McConnell of Kentucky promising to move quickly to confirm Comey's replacement.
Underscoring the abruptness of the firing, the White House apparently had not even begun to field candidates to replace Comey and said it would begin the search "immediately."
Comey, 56, is only the second FBI chief to be fired. FBI directors normally are appointed to serve a single, 10-year term.
Comey was popular within the agency and was well-regarded by both Republicans and Democrats when former President Barack Obama appointed him four years ago.
The White House in defending its ouster of Comey released a highly critical memo written by Rosenstein that found fault with Comey's handling of the Clinton e-mail investigation on many points.
"I cannot defend the director's handling of the conclusion of the investigation of Secretary Clinton's e-mails, and I do not understand his refusal to accept the nearly universal judgment that he was mistaken" to make an announcement about the investigation just days before the election, Rosenstein wrote.
With reporting by AP, AFP, and Reuters