The media conference was the first time the President had faced questions since the Justice Department named a special counsel to probe Russia’s involvement in the 2016 election.

“Well I respect the move, but the entire thing has been a witch hunt,” President Trump said when asked about the investigation.

“There is no collusion between, certainly myself and my campaign. But I can only speak for myself and the Russians, zero.

“I think it divides the country, I think we have a very divided country because of that and many other things. So I can tell you that we want to bring this great country of ours together.”

The President’s comments come after he angrily denounced the appointment of former FBI boss Robert Mueller to head the Russia investigation in a series of angry tweets as “the single greatest witch hunt of a politician” in US history.

“With all of the illegal acts that took place in the Clinton campaign & Obama Administration, there was never a special councel (sic) 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 President corrected his spelling error in a later Twitter post.

With all of the illegal acts that took place in the Clinton campaign & Obama Administration, there was never a special counsel appointed!

— Donald J. Trump (@realDonaldTrump) May 18, 2017

This is the single greatest witch hunt of a politician in American history!

— Donald J. Trump (@realDonaldTrump) May 18, 2017

At at a luncheon with a group of television news anchors later Friday morning, suggested that the investigation, which will give Mr Mueller sweeping new powers, was motivated by an attempt to tarnish his election victory last year.

“It also happens to be a pure excuse for the Democrats having lost an election that they should have easily won because of the Electoral College being slanted so much in their way. That’s all this is,” he said.

President Trump’s comments were in contrast to his measured statement shortly after Mr Mueller’s appointment, in which he said “a thorough investigation will confirm what we already know – there was no collusion between my campaign and any foreign entity”.

They also come after he made a speech on Thursday saying “no politician in history” had been treated worse or more unfairly than he has.

Deputy Attorney General Rod Rosenstein appointed Mr Mueller after a succession of dramatic developments that brought questions over Russia’s alleged meddling in the election and possible collusion by the Trump campaign to a boil.

They included President Trump’s firing of FBI Director James Comey, reports that Mr Trump had previously pressured Mr Comey to end a probe of former national security adviser Michael Flynn, and the President discussing sensitive information on Islamic State with the Russian foreign minister.

Mr Mueller will be armed with sweeping powers, including the right to subpoena documents or interview the President as he builds a case centred on the question of whether any Trump associates colluded with Moscow to influence the course of the election or committed any crimes.

Democratic Senator Amy Klobuchar responded by saying, “This is a truth hunt.”

Mr Rosenstein, the second ranking Justice Department official, named Mr Mueller amid mounting pressure in Congress for an independent investigation beyond existing FBI and congressional probes into the Russia issue.

Mr Mueller’s appointment was not expected to affect the FBI or congressional investigations.

Senate Democratic Leader Chuck Schumer said Mr Comey should still appear before congressional committees that have invited him to testify.

A key issue Mr Mueller may have to tackle is whether President Trump has committed obstruction of justice, an offence that could be used in any effort in Congress to impeach him and remove him from office.

Mr Trump cited displeasure with the FBI’s Russia probe as a factor in dismissing Mr Comey.

In addition, Mr Comey wrote a memo detailing President Trump’s comments to him in February saying “I hope you can let this go,” referring to the Flynn probe, a source who saw the memo said on Tuesday.

– With agencies