Comey confirmed the Federal Bureau of Investigation has been investigating since last July possible Russian government efforts to interfere in the election, including any links between Trump's campaign and Moscow.
"As you know our practice is not to confirm the existence of an ongoing investigation", Comey said at the beginning of the hearing.
US investigators say Russian President Vladimir Putin ordered the hacking into the computers at the Democratic National Committee. He made the claim two days after Attorney General Jeff Sessions, who had met with Russia's USA ambassador last fall, said he would remove himself from any investigation of Russian interference in the election.
He also said his committee, as well as a similar committee in the Senate, was determined to identify and prosecute any current and/or former US officials - he said they were "numerous" - who had leaked potentially classified information to the media.
Mr Trump took to Twitter before the hearing began, accusing Democrats of making up allegations about his campaign associates' contact with Russian Federation during the election. Comey and Rogers deflected many questions about specific parts of the probe or surveillance activities, saying they could not publicly discuss sensitive information. Flynn later misled Vice President Mike Pence about the nature of the discussion, leading to his resignation last month as President Donald Trump's national security adviser. Comey also said he was unaware of any evidence supporting Trump's allegations that Obama wiretapped Trump Tower during the campaign.
The ranking Democratic congressman on the House Intelligence Committee hit back at President Donald Trump's claim that hearings into his campaign's ties to Russian Federation were "FAKE NEWS". Democrats pressed for details on the status of the FBI's investigation, while Republicans repeatedly focused on news coverage and possible improper disclosures of classified information developed through surveillance.
Asked by Rep. Adam Schiff (D-CA) if he or his counterparts ever requested the British to wiretap on behalf of Obama, Rogers said he hadn't and that would be against an agreement that has been in place for decades. He added that "we do not yet know" if Russian Federation had any help from American citizens, including Trump associates, as it allegedly waged the influence campaign. That's a hacker believed to have ties to the Russian government who said he hacked the Democratic National Committee during the campaign.
Republicans on the committee used their questions mostly to press Rogers and Comey about leaks of potentially classified information and surveillance of US citizens. Comey said Moscow had always been opposed to Trump's election rival, former secretary of state Clinton.
Trump blamed Democrats on Monday for stirring concerns about Russian Federation, but top Republican lawmakers John McCain, Lindsey Graham and Marco Rubio, among others, have publicly said they want to find out more about Russia's role in the election.
Trump's next two tweets showed video of the pair of intelligence officials discussing leaks, which Trump and Republicans on the intelligence committee repeatedly condemned as illegal and risky.
A White House official told CNN as the hearing was ongoing that "nothing has changed" based on revelations from Comey's testimony.
"There was circumstantial evidence of collusion; there is direct evidence, I think, of deception", Schiff said on NBC's "Meet the Press".
His "desperation demands answers to our original question: what is Russia's political, personal and financial grip on the Trump Administration?" His first National Security advisor, Michael Flynn, resigned last month following revelations that he misled White House officials about whether he discussed sanctions on Russia in conversations with Sergey Kislyak, the Russian ambassador to the us, before Trump took office. The Obama administration brought those sanctions in response to the alleged meddling. Sessions, a former senator and Trump campaign advisor, admitted that he met with the ambassador during the campaign but said he did so in his capacity as a lawmaker.