President Donald Trump lashed out again Thursday at the ongoing inquiries into his presidential campaign and Russia, counteracting an earlier, more measured response from the White House.

On Wednesday, the Justice Department appointed former FBI Director Robert Mueller as a special counsel to lead the probe into alleged Russian interference in the 2016 U.S. election. Among the things being investigated are possible links between Trump campaign associates and the Kremlin.

In a pair of Thursday morning tweets, Trump asked why no special counsel was appointed for what he called "all of the illegal acts" of Hillary Clinton's campaign and the Obama administration. He then called the Russia investigation "the single greatest witch hunt in American political history."

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

Trump's tweets took a starkly different tone from the official statement the White House released in his name Wednesday night:

"As I have stated many times, a thorough investigation will confirm what we already know — there was no collusion between my campaign and any foreign entity. I look forward to this matter concluding quickly. In the meantime, I will never stop fighting for the people and the issues that matter most to the future of our country."

It marks at least the third time in just over a week that Trump has either contradicted or muddled a statement from his White House.

Trump last week fired ex-FBI Director James Comey, whose agency was investigating the president's campaign, and reports since then have raised questions about whether he had tried to influence the investigation.

After Trump ousted Comey, the White House first said the president did so because of a Justice Department memo criticizing the FBI chief's performance. Later, though, Trump told NBC News that he would have fired Comey "regardless" and was thinking of the "Russia thing" when he did so.

White House officials also vehemently denied reports that Trump shared highly classified information in a meeting with Russian diplomats last week. But in later tweets, the president said he did share information about threats with the Russian officials, though he neither confirmed nor denied if it was classified.

The mixed messages come as rumors have swirled about a possible shake-up of White House communications staff.

On Wednesday, Trump complained in the middle of a U.S. Coast Guard Academy commencement speech that he has been "treated worse" than any politician "in history."