U.S. Attorney General Jeff Sessions has resigned as the country's chief law enforcement officer at the request of President Donald Trump, throwing the future of the special counsel's Russia investigation into uncertainty.
The White House said Sessions resigned in a letter to Trump on November 7 and that the president had accepted his resignation as chief of the Justice Department -- a move that immediately raised concerns from Democrats, who called for protection for the probe conducted by Special Counsel Robert Mueller.
House Democratic leader Nancy Pelosi called it a "blatant attempt" to undermine the Russia probe, while Senate Democratic leader Chuck Schumer tweeted that "clearly, the president has something to hide."
The Justice Department has the ultimate authority over Mueller's investigation into Russia's alleged interference in the 2016 presidential election and interactions between Trump associates and Russian officials.
Russia denies meddling in the election, and Trump denies any "collusion" with Russia.
Sessions, a Republican and former Alabama senator, has been the focus of public attacks by Trump, who criticized him for recusing himself from the Russia investigation because of his role on the Trump campaign team before becoming attorney general.
Trump announced in a tweet that Sessions' chief of staff, Matthew Whitaker, will become the new acting attorney general. Whitaker, a former Republican politician, has publicly called for limits on the Mueller probe.
As Sessions' deputy, Rod Rosenstein has been the authority over Mueller's probe, but multiple media outlets are reporting that he has officially been removed from oversight of the investigation.
A spokeswoman for the Justice Department said that the acting attorney general -- meaning Whitaker -- was in charge of "all matters" within the department, including the Russia probe.
Democratic Representative Jerry Nadler, who will likely become chairman of the House Judiciary Committee -- which has congressional oversight over the Mueller probe -- immediately responded to Sessions' resignation by demanding an explanation for the change.
"Americans must have answers immediately as to the reasoning behind" Trump’s move to remove Sessions, he said.
"Why is the President making this change and who has authority over Special Counsel Mueller’s investigation? We will be holding people accountable," he tweeted.
Schumer called it "paramount" that Mueller's status be protected by the new attorney general.
The senator said he found the timing of Sessions' departure "very suspect" and suggested it would cause a "constitutional crisis" if Trump made the move as a "prelude" to limiting the Russia investigation.
He called on Whitaker to recuse himself from the Russia probe because of previous comments about the investigation, echoing calls from other top Democrats.
In her tweet, Pelosi, who is likely to become House speaker under the new Democratic-controlled Congress, wrote that "It is impossible to read Attorney General Sessions' firing as anything other than another blatant attempt by Donald Trump to undermine & end Special Counsel Mueller's investigation."
Earlier, at a White House news conference, Trump said the Mueller investigation was not good for the United States.
"It should end, because it is very bad for the country," Trump told reporters.
When asked if he would fire Mueller, as some critics have feared, Trump said, "I could have ended it any time I wanted, [but] I didn't."
"I could fire everybody right now, but I don't want to stop it because, politically, I don't like stopping it."
He said he was "not concerned about anything with the Russian investigation, because it is a hoax."
"They're wasting a lot of money, but I let it go on. I could end it right now," he added.