WASHINGTON >> President Donald Trump acknowledged for the first time today that he is under federal investigation as part of the expanding probe into Russia’s election meddling. He lashed out at a top Justice Department official overseeing the inquiry, reflecting his mounting frustration with the unrelenting controversy that has consumed his early presidency.

“I am being investigated for firing the FBI Director by the man who told me to fire the FBI Director! Witch Hunt,” the president wrote on Twitter.

His morning missive apparently referred to Rod Rosenstein, the deputy attorney general whose role leading the federal investigation has become increasingly complicated. The White House has used a memo he wrote to justify Trump’s decision to fire FBI Director James Comey, but that Trump action may now be part of the probe. Thursday night, Rosenstein issued an unusual statement complaining about leaks in the case.

Trump advisers and confidants describe the president as increasingly angry over the investigation, yelling at television sets in the White House carrying coverage and insisting he is the target of a conspiracy to discredit — and potentially end — his presidency. Some of his ire is aimed at Rosenstein and investigative special counsel Robert Mueller, both of whom the president believes are biased against him, associates say.

Dianne Feinstein, top Democrat on the Senate Judiciary Committee, said she was “increasingly concerned” that Trump will fire both Mueller and Rosenstein.

“The message the president is sending through his tweets is that he believes the rule of law doesn’t apply to him and that anyone who thinks otherwise will be fired,” Feinstein said. “That’s undemocratic on its face and a blatant violation of the president’s oath of office.”

Aides have counseled the president to stay off Twitter and focus on other aspects of his job. They have tried to highlight the positive reviews he received Wednesday when he made a statesman-like appearance in the White House to address the nation after Rep. Steve Scalise was shot during a congressional baseball practice.

Yet Trump’s angry tweets today underscored the near-impossible challenge his advisers and legal team have in trying to get him to avoid weighing in on an active probe.

The president has denied that he has any nefarious ties to Russia and has also disputed that he’s attempted to block the investigation into his campaign’s possible role in Russia’s election-related hacking. It was unclear whether his tweet about being under investigation was based on direct knowledge or new media reports that suggest Mueller is examining whether the president obstructed justice by firing Comey.

The tweets came shortly after Rosenstein issued his unusual statement that appeared to be warning about the accuracy of such reports.

“Americans should be skeptical about anonymous allegations,” Rosenstein said. “The Department of Justice has a long-established policy to neither confirm nor deny such allegations.”

The department would not comment on the record on whether Trump, who has repeatedly complained about leaks on the case, requested the statement. But a department official said no one asked for the statement and Rosenstein acted on his own. The official demanded anonymity because the official was not authorized to be named discussing the deliberations.

Trump has told associates he has the legal authority to fire Mueller, a move that might first require firing Rosenstein and would certainly intensify the uproar over the investigation. Though some in the White House have preached caution, fearing a repeat of the firestorm over Comey’s firing, many in Trump’s orbit — including his son Donald Trump Jr. and adviser Newt Gingrich — have deemed Mueller biased and worthy of dismissal.

Several White House officials and Trump associates insisted on anonymity in order to discuss the president’s views of the unfolding investigation.

Rosenstein has been overseeing the Russia probe since shortly after Attorney General Jeff Sessions recused himself. But Rosenstein, too, may ultimately have to hand off oversight given his role in Trump’s decision to fire Comey.

Earlier this month, Rosenstein told The Associated Press that “if anything that I did winds up being relevant to his investigation then, as Director Mueller and I discussed, if there’s a need from me to recuse, I will.”

Trump’s tweets came after the top lawyer for his transition team warned the organization’s officials to preserve all records and other materials related to the Russia probe. An official of Trump’s transition confirmed the lawyer’s internal order, which was sent Thursday.

The order from the general counsel for the transition team casts a wide net on documents that could shed light on ties between Trump’s presidential campaign and representatives of Russia’s government. The order also covers separate inquiries into several key Trump associates including former National Security Adviser Michael Flynn, campaign adviser Paul Manafort, foreign policy aide Carter Page and outside adviser Roger Stone.

The White House has directed questions for details to outside legal counsel, which has not responded.

Vice President Mike Pence has also hired a private lawyer to represent his interests in the expanding probe. Pence headed the Trump transition until Inauguration Day.

Associated Press writers Steve Braun, Sadie Gurman, Eric Tucker, Mary Clare Jalonick and Vivian Salama contributed to this report.