U.S. President Donald Trump has repeated his denials that there was any collusion between his presidential campaign and agents of the Russian government.
Speaking briefly to reporters as he left the White House on December 2, Trump said there was "absolutely no collusion."
Later, Trump amplified his remarks in a post on Twitter.
"I had to fire General Flynn because he lied to the Vice President and the FBI," Trump wrote. "He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!"
The comments came one day after Trump's former national security adviser, Michael Flynn, pleaded guilty to lying to the FBI about his contacts with the Russian ambassador during the transition period between the November 2016 election and the time Trump took office in January 2017.
According to media reports, Flynn has agreed to testify that he was ordered by an unnamed senior transition team official to establish connections with the Russian government.
Flynn faces up to five years in prison for the charge of lying to the FBI, but his sentencing could also depend on the extent of his cooperation with investigators.
Flynn resigned as national security adviser in February after serving in the post just 24 days amid revelations that he misled Vice President Mike Pence about his contacts with then-Russian Ambassador to the United States Sergei Kislyak.
Trump's lawyer, Ty Cobb, released a statement on December 1 saying Flynn's guilty plea does not implicate anyone other than Flynn.
"The false statements involved [in the indictment] mirror the false statements to White House officials which resulted in [Flynn's] resignation in February," Cobb's statement said.
Flynn is the fourth person to be criminally charged in connection with the investigation. Former Trump campaign chairman Paul Manafort and his business associate Rick Gates were indicted in October on charges that included conspiracy and lying to federal agents. Former foreign policy adviser George Papadopoulos, meanwhile, has pleaded guilty to lying to FBI agents and was cooperating with Mueller’s investigators.
In January, a U.S. intelligence finding charged that the Russian government undertook a concerted effort to influence the 2016 election in favor of Trump.
With reporting by AP and Reuters