His investigation then grew to include looking at whether President Trump fired FBI Director James Comey because he was unwilling to back off the Russian Federation investigation. Trump exclaimed on Twitter, referring to the investigation as a "Witch Hunt".
"Mr. Trump's apparent reference to Mr. Rosenstein, who oversees the Russian Federation investigation because Attorney General Jeff Sessions recused himself from it, came just hours after an oddly worded statement from Mr. Rosenstein complaining about leaks in the case".
Trump's tweet could be targeting Deputy Attorney General Rod Rosenstein, who appointed former Federal Bureau of Investigation director Robert Mueller as special counsel to oversee the probe into Russia's intervention into the last year's presidential polls.
The Washington Post also claims that right after Comey gave this document to Mueller, Mr. Mueller then opened an investigation of President Trump on whether of not he obstructed justice in firing James Comey.
The Washington Post, citing unidentified officials, has reported that special counsel Robert Mueller is investigating U.S President Donald Trump for a possible obstruction of justice as part of the widening probe.
Robert Mueller, the man chosen to take over the inquest as special investigator, had started investigating into president Trump's behaviour. "Nice", Mr Trump wrote on Twitter earlier, later repeating his accusation the probe was a "witch hunt". Earlier this week the Washington Post released a story reporting Mueller is investigating President Trump for obstruction of justice.
Mr. Trump's latest tweets drew a concerned statement from Sen. On Friday, the President tweeted he was under "investigation", which he called a "witch hunt" in another tweet.
Trump's tweets have recently looked an very bad lot like what a reporter said were GOP talking points meant to combat the Post's report.
Until recently the investigation was focused exclusively on Russia's meddling and possible collusion with the Trump campaign during the 2016 election.
"This is a political fight and he's going to fight it", a White House official said regarding president's Friday's tweets.
The White House confirmed Mr Mueller was among the candidates the president interviewed to replace Mr Comey. It's all prompted officials and outside advisers to wonder if his actions have only made things worse for his administration as an investigation into ties between his campaign and Russian Federation continues to widen.
On Thursday, Russian President Vladimir Putin said 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".
"Why is that Hillary Clintons family and Dems dealings with Russian Federation are not looked at, but my non-dealings are?" he asked.