Comey, whom Trump fired last week, oversaw a federal investigation of Flynn that centers on his ties to Russian Federation while he worked on Trump's campaign past year.
The information had been supplied by a US ally in the fight against the Islamic State militant group, the officials said.
Top Democratic Senator Chuck Schumer said he was "shaken" by the New York Times report.
Putin's remarks come as Washington was reeling over revelations late Tuesday that Trump personally appealed to FBI Director James Comey to abandon the bureau's investigation into National Security Adviser Michael Flynn.
"If these reports are true, the president's brazen attempt to shut down the FBI's investigation of Michael Flynn is an assault on the rule of law that is fundamental to our democracy", Democratic Leader Nancy Pelosi said in a statement. "It is clear former FBI Director Comey should testify before Congress". "This is what caused President Nixon to resign from office".
It is illegal for private citizens to conduct United States diplomacy.
White House officials have stressed that the Russian Federation probe had nothing to do with Trump's firing of Comey, although Trump himself has suggested in interviews that it was at least partly a motivation.
Russia President Vladimir Putin offered Wednesday to turn over to Congress records of President Donald Trump's discussions with Russian diplomats in which Trump is said to have disclosed classified information. The White House denied the president did anything improper in his meeting with the Russians.
The president defended his actions on Twitter Tuesday, saying he has the right to share facts pertaining to terrorism and airline security.
So, yeah, we've got another 5 p.m. release of a Big Big Story based on anonymous sources who didn't show the Times reporter the memo, but just read some selected parts of it.
Islamic State, or ISIS, holds territory in Iraq and Syria and is a common foe of Moscow and Washington. Granted, one might think he would care when USA interests (and perhaps lives) are on the line, but we've seen no evidence of that; that "officials expressed concern with Trump's handling of sensitive information as well as his grasp of the potential consequences" is consistent with everything we've seen from him in the campaign, during the transition and after he took office.
"The president wasn't even aware of where this information came from. He wasn't briefed on the source and method of the information either", McMaster told reporters. "What the president shared was wholly appropriate", he said.
Flynn has been at the centre of that investigation shortly after Trump's arrival to the White House. "I think it'd be a fascinating job, it's a challenging job, and you need someone really determined and focused, a great communicator in there with deep knowledge to be able to handle that position".
"Something's not happening day after day".
From my old vantage point of White House Counsel's office, I want to focus on two particular issues: Trump's White House contacts policy and the Take Care Clause.
A new report could bring more potential trouble for President Trump.
USA manufacturing production recorded its biggest increase in more than three years in April but housing starts posted a surprise fall to five-month lows.
ANALYST TAKE: "This adds to a darkening cloud of controversy and disarray hovering over the White House", said Mike van Dulken, an analyst at Accendo Markets. "The American people deserve answers about President Trump's conduct".
There is no sign the FBI's Russian Federation investigation is closing.
Republicans still call the shots in Congress, however, and it's a significant leap to get them to abandon the Trump presidency and any hope of advancing their agenda for the foreseeable future.
Other Republicans, however, expressed concern.
"This trip combines so many different things and actors that the question is going to be what's the message that he wants to communicate when he's out there", said Lanhee Chen, who advised Republican Mitt Romney's presidential campaign in 2012 and Marco Rubio's in 2016. But they came to despise Comey for his leading man role in a later drama, the probe into Hillary Clinton's email server.
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