President Trump took to Twitter on Thursday to offer his first comments on news that he is being examined for possible obstruction of justice — an investigation he dismissed as part of “phony” accusations of collusion between his campaign and Russia last year.

“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,” Trump said in a tweet shortly before 7 a.m.

“Nice,” he added.

An hour later, Trump fired off another tweet, saying: “You are witnessing the single greatest WITCH HUNT in American political history - led by some very bad and conflicted people!”

He did not name the “bad and conflicted people.”

The Washington Post reported Wednesday that the special counsel overseeing the investigation into Russia’s role in the 2016 election is interviewing senior intelligence officials as part of a widening probe that now includes an examination of whether Trump attempted to obstruct justice, according to officials.

The special counsel overseeing the investigation into Russia's role in the 2016 election is interviewing senior intelligence officials to determine whether President Trump attempted to obstruct justice, officials said. (Patrick Martin,McKenna Ewen/The Washington Post)

The move by special counsel Robert S. Mueller III to investigate Trump’s conduct marks a major turning point in the nearly year-old FBI investigation, which until recently focused on Russian meddling during the presidential campaign and on whether there was any coordination between the Trump campaign and the Kremlin.

The White House has recently made a practice of referring questions related to the investigation to Trump’s personal lawyer, and aides and associates have urged the president to refrain from commenting on the case on Twitter.

On Wednesday night, a spokesman for Trump’s lawyer did not dispute that Trump was under examination but decried what he said were leaks that led to the story.

“The FBI leak of information regarding the president is outrageous, inexcusable and illegal,” said Mark Corallo, a spokesman for Marc Kasowitz, Trump’s personal lawyer.

Trump, who celebrated his 71st birthday Wednesday, refrained from commenting until Thursday morning.