Donald Trump resorted to Twitter to slam a report that special counsel Robert Mueller is investigating the President for possible obstruction of justice.

In a series of tweets, Trump on Thursday said: "They made up a phony collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phony story. Nice," reports Efe news.

Shortly thereafter, he followed that up with another tweet, in which he returned to one of his main themes regarding the ongoing probe: "You are witnessing the single greatest witch hunt in American political history – led by some very bad and conflicted people."

The tweets were clear signs of the president's frustration and anger over the revelation, published on Wednesday evening in The Washington Post, about the investigation by Mueller, who is heading an independent probe into alleged Russian interference in the 2016 election.

A few hours later, Trump again tweeted, this time attempting to divert attention toward his former rival, former Secretary of State Hillary Clinton, first saying: "Why is that Hillary Clinton's family and Democrats dealings with Russia are not looked at, but my non-dealings are?"

In a second tweet, he continued with "Crooked Hillary destroyed phones with hammer, 'bleached' emails, and had husband meet with (Attorney General Loretta Lynch) days before she was cleared and they talk about obstruction?"

The Washington Post, citing anonymous sources, had reported some hours earlier that Mueller, who is probing Russia's election interference and the possible links between Moscow and Trump's campaign, had added a key element to that probe, namely that the President would now be under investigation for obstruction of justice.

If the report is true and if it is confirmed that Trump obstructed justice by trying to get former Federal Bureau of Investigation (FBI) Director James Comey, and perhaps others, to end the Russia probe, that could lead to the President's impeachment by Congress, something that many Democratic lawmakers say they would pursue if circumstances warrant.

Meanwhile, the White House said on Thursday that it would have no comment about the revelation, with deputy Press Secretary Sarah Sanders simply referring all questions to the President's personal lawyer, Marc Kasowitz.

Kasowitz said on Wednesday that leaking FBI information about the president was "outrageous, inexcusable and illegal", although he did not question the content of the article.