US Attorney Preet Bharara of New York said today he had been fired after he defied a Justice Department request to resign as the Trump administration cleared out federal prosecutors who served under former President Barack Obama.
"I did not resign. Moments ago I was fired," Mr Bharara wrote on Twitter.
The Justice Department declined to comment.
Mr Bharara, whose jurisdiction as US attorney for the Southern District of New York included Manhattan, has handled a string of high-profile corruption and white-collar criminal cases.
He was one of 46 Obama administration holdovers who were asked to resign by the Justice Department yesterday.
Like all of the nation's 93 US attorneys, Mr Bharara is a political appointee who is typically replaced when a new president takes office.
Mr Bharara told reporters in November that Mr Trump had asked him to stay on, and a source familiar with the situation said that he was confused by the Justice Department's request that he step down.
Mr Bharara's office did not immediately respond to a request for a comment today.
Attorney General Jeff Sessions' decision to replace so many sitting attorneys at once has raised questions about whether that would hinder the Trump administration's ability to enforce the nation's laws. Career attorneys will carry on that work until new US attorneys are put in place, the Justice Department said.
Mr Trump has asked two US prosecutors to remain on the job, according to the Justice Department.
US Attorney Rod Rosenstein of Maryland has been asked to stay on as the Senate considers his nomination to serve as the No. 2 Justice Department official, and US Attorney Dana Boente of Virginia, who is temporarily serving in that position, has also been asked to remain.
A White House spokeswoman said she did not know whether other US attorneys would be asked to remain in office.
Meanwhile, Mr Trump praised the US Secret Service for a "fantastic job" following their late-night arrest of an intruder who breached the White House grounds while the president was there.
After scaling an outer perimeter fence at the Washington executive residence just before midnight last night, the suspect was arrested by uniformed secret service officers, officials at the agency said.
Speaking to reporters today at his Virginia golf club, Mr Trump said the "secret service did a fantastic job last night" adding that the intruder "was a troubled person".
Authorities did not find dangerous materials inside a backpack that the intruder had. The grounds of the presidential complex were also deemed safe.
Mr Trump, who is spending the weekend in the nation's capital, was in the White House at the time of the intrusion. He was apprised of the situation, White House spokesman Sean Spicer told journalists today.
John Kelly, head of the US Department of Homeland Security, was briefed on the security breach.
The White House has seen a string of high-profile trespassing incidents in recent years.
In one notable 2014 incident, while Barack Obama was president, a disturbed army veteran jumped the White House fence, sprinted across the lawn and entered the building with a knife in his pocket.
