President Trump on Tuesday thanked Yahoo News reporter Michael Isikoff, one of the first to report on the so-called Steele dossier about possible connections between Russia and Trump, for comments Isikoff made raising doubts about the veracity of the document.

The president took Isikoff's comments as a chance to target special counsel Robert Mueller's investigation into possible collusion between Russia and the Trump campaign, saying the probe should "be ended immediately."

"Thank you to Michael Isikoff, Yahoo, for honesty. What this means is that the [Foreign Intelligence Surveillance Act] WARRANTS and the whole Russian Witch Hunt is a Fraud and a Hoax which should be ended immediately. Also, it was paid for by Crooked Hillary & [Democratic National Committee]!" Trump said in a series of tweets Tuesday morning.

"Michael Isikoff was the first to report Dossier allegations and now seriously doubts the Dossier claims. The whole Russian Collusion thing was a HOAX, but who is going to restore the good name of so many people whose reputations have been destroyed?" he added.

Isikoff, the co-author of the book "Russian Roulette: The Inside Story of Putin's War on America and the Election of Donald Trump," criticized parts of the dossier Monday while appearing on John Ziegler's Free Speech Broadcasting podcast.

"In broad strokes, Christopher Steele was clearly onto something, that there was a major Kremlin effort to interfere in our elections, that they were trying to help Trump's campaign, and that there was multiple contacts between various Russian figures close to the government and various people in Trump's campaign," Isikoff said.

But the reporter said that there is not any "evidence to support" some of the details.

"When you actually get into the details of the Steele dossier, the specific allegations, we have not seen the evidence to support them, and, in fact, there's good grounds to think that some of the more sensational allegations will never be proven and are likely false," he added.

The dossier, compiled by former British intelligence agent Christopher Steele, detailed efforts by Russia to coordinate with the Trump campaign to meddle in the 2016 presidential election. It also includes salacious details about possible blackmail Russia compiled on Trump during his visits to Moscow.

While several details of the dossier have been confirmed, according to the Senate Intelligence Committee, some of the more sensational details have not yet been verified.

Trump and his allies have long criticized the document as a work of fiction, noting that it was paid for, in part, by 2016 Democratic presidential nominee Hillary Clinton's campaign and the Democratic National Committee.