US President Donald Trump has claimed "total and complete vindication" after ousted FBI director James Comey said he was not personally under investigation in a probe into Russian interference in last year's US election.
The early-morning tweet was President's Trump's first response to Comey's testimony before a Senate committee in which he accused the president of lies and defamation.
During almost three hours of extraordinarily frank statements before the committee, Comey described himself as "stunned" by Trump's "very disturbing" and "very concerning" behavior in several meetings.
Detailing one-on-one talks with a sitting president -- which under normal circumstances are private -- Comey said he took painstaking notes for fear Trump might "lie" about the unusual encounters.
The testimony painted a devastating picture of an untrustworthy president, who at best unknowingly shred the norms of office by pressing Comey on a probe into Russian election meddling, and at worst may have criminally obstructed justice.
Pundits and legal experts were divided on whether President Trump's actions rose to the level of obstruction of justice, a potentially impeachable offense, while Comey said that decision was now in the hands of a high-powered special prosecutor.
President Trump will face the media on Friday when he holds a joint press conference with the visiting president of Romania.
On Thursday, he defiantly told supporters at a scheduled event: "We are going to fight and win."
WATCH: Comey stunned by Trump conversation
'Loyalty'
During one White House dinner, Comey recalled that the president asked him for "loyalty" and to lay off his former national security advisor Michael Flynn -- who is under criminal investigation over his Russia ties -- imploring Comey to "let this go."
Comey said he believed he was sacked over his handling of the Russia investigation, which includes probing allegations that Trump's campaign colluded with Moscow to tip the election to the real estate tycoon.
"I was fired in some way to change, or the endeavor was to change the way the Russia investigation was being conducted. That is a very big deal," Comey told senators.
Easing months of speculation, Comey confirmed that President Trump was not personally under investigation when he left the FBI last month.
The White House and Trump's lawyers expressed vindication over some parts of Comey's testimony and lashed out at others.
"I can definitely say the president is not a liar and frankly am insulted by that question," White House spokeswoman Sarah Huckabee Sanders said.
President Trump's lawyer Marc Kasowitz said the president "never told Mr Comey 'I need loyalty, I expect loyalty' in form or substance," rejecting the key allegation.
Deploying President Trump's trademark bareknuckle style, Kasowitz also suggested the ousted lawman should be prosecuted for leaking "privileged information."
'Lies, plain and simple'
A visibly aggrieved Comey kicked off his testimony with a bid to set the record straight about the state of the bureau he led until he was sacked last month.
"Although the law requires no reason at all to fire an FBI director, the administration then chose to defame me and more importantly the FBI by saying that the organization was in disarray, that it was poorly led, that the work force had lost confidence in its leader," he charged.
"Those were lies plain and simple," Comey said, firing a shot of tension through hearing room 216 of the Senate's Hart building, which stood silent except for the shutter clicks of photographers capturing the political theater.
Democrats are intent on determining whether President Trump's actions amounted to obstruction of justice, while Republicans zeroed in on Comey's admission he assured the president he was not personally an FBI investigation target.
President Trump abruptly fired Comey as director of the Federal Bureau of Investigation on May 9, admitting later that the Russia probe was on his mind at the time.
In a written statement, Comey described his mounting discomfort in the weeks leading up to his dismissal as President Trump pulled him aside in person and phoned to press him on the probe into his campaign associates and possible collusion with Russia.
WATCH: Trump's lawyer disputes Comey claims
'A big deal'
At a private White House dinner on January 27, just days after the billionaire took office, Comey said President Trump appeared to want to "create some sort of patronage relationship" with him.
"The president said, 'I need loyalty, I expect loyalty.' I didn't move, speak, or change my facial expression in any way during the awkward silence that followed," Comey said.
In an Oval Office tete-a-tete the following month, Comey said President Trump pressed him to drop the FBI investigation into Flynn, who had been fired for lying to the vice president about unreported conversations with the Russian ambassador.
Harvard Law School professor Mark Tushnet said onlookers should keep in mind that Comey knows much more than he can say.
"He's saying that when he looks at all the evidence that he knows, that he draws the conclusion that the president was trying to pull him off the investigation of Flynn.
"It's a pretty powerful statement that an investigator with his background (says) when I look at this investigation, this is what I conclude. So his statement is a big deal," he said.
But Republican House Speaker Paul Ryan appeared to sympathize with President Trump, telling a news conference that "the president's new at this."
"He probably wasn't steeped in the long-running protocols that establish the relationships between (Department of Justice), FBI and White Houses. He's just new to this."
