WASHINGTON — President Trump acknowledged publicly for the first time on Friday that he was under investigation in the expanding inquiry into Russian influence in the election, and he appeared to attack the integrity of the Justice Department official in charge of leading it.
In an early-morning tweet, the president declared that he was “being investigated” for his decision to fire James B. Comey, the former F.B.I. director. And he appeared to accuse Rod J. Rosenstein, the deputy attorney general, of leading a “witch hunt.”
The tweet was the first explicit acknowledgment by the president that Robert S. Mueller III, the special counsel for the Russia inquiry, had begun examining whether Mr. Trump’s firing of Mr. Comey last month was an attempt to obstruct the investigation.
And Mr. Trump’s apparent reference to Mr. Rosenstein, who oversees the Russia investigation because Attorney General Jeff Sessions recused himself from it, came just hours after an oddly worded statement from Mr. Rosenstein complaining about leaks in the case.
In the statement, Mr. Rosenstein wrote, without further explanation, that “Americans should exercise caution before accepting as true any stories attributed to anonymous ‘officials,’ particularly when they do not identify the country — let alone the branch or agency of government — with which the alleged sources supposedly are affiliated.”
The latest tweet came after a series of others in which Mr. Trump continued to complain about the Russia investigations swirling around him, and just hours after members of Congress from both parties gathered at a baseball field to call for unity after the shooting at a Republican baseball practice this week.
In two other early-morning tweets, the president insisted that no one has found any “proof” that he colluded with Russians to meddle with the 2016 presidential elections, and he once again assailed the news media.
Mr. Trump’s claim to have 100 million social media followers is an exaggeration based on adding his followers on Twitter, Facebook and Instagram — many of whom are most likely the same people.
But however many people actually follow him on social media, the president clearly views them as a refuge from the barrage of newspaper headlines and cable news stories about the Russia investigations.
In just the past 48 hours, news organizations have reported that Mr. Mueller is investigating whether Mr. Trump obstructed justice by firing Mr. Comey.
The Washington Post reported on Thursday that Mr. Mueller is also investigating the business dealings of Jared Kushner, Mr. Trump’s son-in-law and senior adviser.
Faced with a Russia investigation that appears to be broadening, Mr. Trump appears eager to use Twitter to undermine the credibility of the inquiry and to convince his supporters that they do not need to worry.
In a third tweet Friday morning, Mr. Trump repeated his assertion that the investigations are a “phony Witch Hunt” and bragged that the nation’s economy was improving quickly.