United States President Donald Trump is being investigated by special counsel Robert Mueller for possible obstruction of justice, the Washington Post reported on Wednesday, citing unidentified officials.
On Thursday, Russian President Vladimir Putin said Mr Comey had presented no evidence to prove that Moscow meddled in the United States election, adding that Washington had tried to influence Russian elections "year after year". Trump fired Comey in May.
"You are witnessing the single greatest witch hunt in American political history - led by some very bad and conflicted people!" he continued in another tweet.
Mr Trump is unlikely to face criminal prosecution as a sitting president, but obstruction of justice could be grounds for impeachment. Trump later said he had planned to fire Comey regardless of what recommendation he received from Rosenstein and Attorney General Jeff Sessions, who has recused himself from the Russian Federation investigation.More news: Senate approves new Russia sanctions
Mr Rosenstein took over the investigation into whether Russian Federation tried to tip the U.S. election in favour of Mr Trump after Attorney General Jeff Sessions recused himself in March.
While FBI Director James Comey told President Trump on three separate occasions that he was not personally under investigation for colluding with Russians in the 2016 election, that's NOT necessarily the case anymore.
Seth Moulton, a congressman from Salem in Massachusetts, tweeted, "As the Representative of Salem, MA, I can confirm that this is false", referring to Mr Trump's "witch hunt" whine.
Trump and his White House have offered various explanations for Comey's abrupt ouster, including that he lost the confidence of the bureau's rank and file - a suggestion flatly dismissed by acting director Andrew McCabe.