President Donald Trump on Thursday called the appointment of a special counsel to lead the Russia probe as “the single greatest witch hunt” in U.S. history, hours after he said he looked forward to a thorough investigation. In the face of rising pressure from Capitol Hill, the U.S. Justice Department named former FBI Director Robert Mueller on Wednesday as special counsel to investigate alleged Russian interference in the 2016 U.S. election and possible collusion between Trump’s campaign and Moscow. Trump said in a statement that “a thorough investigation will confirm what we already know, there was no collusion between my campaign and any foreign entity.” In a pair of Twitter posts on Thursday morning, Trump made clear he was unhappy with the latest development to roil his administration. “With all of the illegal acts that took place in the Clinton campaign and Obama Administration, there was never a special counsel appointed!” Trump wrote, misspelling the word counsel as he referred to former President Barack Obama and former presidential candidate Hillary Clinton. “This is the single greatest witch hunt of a politician in American history!” The comments mirrored a speech by Trump on Wednesday, before Mueller’s appointment was announced, in which he said no politician in history “has been treated worse or more unfairly.” Russia has denied U.S. intelligence agencies’ conclusion that it interfered in the election campaign to try to tilt the vote in Trump’s favour. Trump, a Republican, has long bristled at the notion that Russia played any role in his November election victory and has denied any collusion between his campaign and Moscow. The appointment of a special counsel to take over the Russia probe was widely praised by Democrats and Trump’s fellow Republicans. Republican Representative Charlie Dent said there was no question the Russians meddled in the election. The goal of the special counsel probe, he said, was to determine whether there was collusion between Trump associates and Russia to do so. “I believe that’s why we’re having this investigation, to find out if in fact there was collusion. “I certainly hope there wasn’t any but if there is there are going to be very serious consequences,” Dent told CNN. Moments before Trump weighed in on Twitter, Democratic Senator Joe Manchin welcomed the special counsel investigation and said it was important to get facts in the Russia probe. “I am not on a witch hunt. I am on a fact-finding mission,” he said on CNN.