WASHINGTON - James Comey said on Thursday he was disturbed by US President Donald Trump's bid to get him to drop a probe into the former national security adviser, but the FBI's fired former director would not say whether he thought the president sought to obstruct justice.Comey told US lawmakers in the most eagerly anticipated US congressional hearing in years that the Trump administration had told lies and defamed him and the FBI after the president dismissed him on May 9.Comey has said Trump asked him in February to drop an FBI investigation of former national security adviser Michael Flynn as part of the probe into alleged Russian meddling in the 2016 US presidential election."I don't think it's for me to say whether the conversation I had with the president was an effort to obstruct. I took it as a very disturbing thing, very concerning," Comey told the Senate Intelligence Committee.The Russia issue has dogged Trump's first months in office, distracting from Trump's policy agenda such as overhauling the US healthcare system and making tax cuts.Comey's accusations could further mire Trump's administration in legal difficulties, as special counsel Robert Mueller and several congressional committees investigate alleged Russian efforts to influence the 2016 presidential election and whether Trump's campaign colluded with Moscow.Russia has denied such interference and the White House has denied any collusion.Trump triggered a political firestorm when he dismissed Comey, and Democrats accused the president of trying to limit the Russia probe.The former FBI head said Trump's administration had defamed him in comments made after his firing by saying that the bureau was in disarray and that the workforce had lost confidence in its leader."Those were lies, plain and simple," Comey said.LOYALTY?Comey said Trump did not attempt to get him to drop the overall Russia investigation, just the part of if that related to Flynn, who the president fired in February for misleading Vice President Mike Pence about the extent of his conversations last year with Russia's ambassador to the United States.As Comey was testifying, a White House source said Trump disputes two key points in Comey's testimony: that he asked the FBI director to let go of the Flynn probe, and that he asked for Comey's loyalty.Trump’s son Donald Trump Jr. fired off a series of tweets attacking Comey but the president himself stayed off social media while the drama played out in Congress.Trump critics say that any efforts by the president to hinder an FBI probe could amount to obstruction of justice.Some legal experts said Comey's testimony could strengthen any impeachment case in Congress to remove Trump from office built on an allegation of obstruction of justice.Laura Donohue, a professor at Georgetown University Law Center said Trump may have broken the law, adding, "If the president directed Comey to drop the investigation, with an improper purpose, then it is a violation of the law."Alan Dershowitz, professor emeritus at Harvard Law School, said, "Nothing I've heard so far changes my view that the president did not obstruct justice."While a sitting president is unlikely to face criminal prosecution, obstruction of justice is an offense that could trigger the impeachment process in Congress.Stocks were little changed as Comey's testimony kicked off, as investors continued to see it as unlikely that Comey's testimony would lead to an end to Trump's presidency.At one point in the hearing, Republican Senator James Risch pressed Comey on whether Trump had actually directed him to drop the Flynn investigation."He did not order you to let it go?" Risch asked."Again, those words are not an order," Comey said. "I took it as a direction. If it is the president of the United States, with me alone, saying 'I hope this' - I took it as 'this is what he wants me to do.' I didn't obey that, but that’s the way I took it," Comey saidWhen asked later on whether he took Trump's comments as a directive, Comey, "Yes."Comey said he did not know if there are tapes of his conversations with Trump but said he hoped there were and that they should be made public. "Release all the tapes. I'm good with it," Comey said.Comey testified that he kept notes after meeting with Trump because "I was honestly concerned that he might lie about the nature of our meeting, and so I thought it really important to document."The White House has given shifting explanations on why Trump fired Comey. Trump has called Comey a "showboat" and a "grandstander" and said he was thinking of "this Russia thing" in dismissing him.