US President Donald Trump attacked the FBI in a series of tweets on Sunday, calling it the "worst in history" and saying that its reputation was "in tatters".
"After years of Comey, with the phony and dishonest Clinton investigation (and more), running the FBI, its reputation is in Tatters - worst in History! But fear not, we will bring it back to greatness," he tweeted.
On Friday, former US National Security Adviser Michael Flynn admitted to the FBI that he had lied about his conversations with the Russian ambassador during the presidential transition.
Special Counsel Robert Mueller is currently investigating whether Trump should be charged with obstruction of justice for firing former FBI director James Comey.
Comey had said Trump had asked him to drop the Flynn probe.