US Democrats said that President Donald Trump's firing of FBI director James Comey may be an effort to undermine the investigation of possible collusion between his team and Russia, demanding an independent investigation.
"I told the president, 'Mr President, with all due respect you are making a big mistake,'" the top Democrat in the Senate, Chuck Schumer, told reporters.
Schumer and others said Comey's shock dismissal was the latest in a series of administration firings that raised red flags about the White House's commitment to probing Russian interference in last year's election, and possible Trump-Russia connections.
"This does not seem a coincidence," Schumer said. "This investigation must be run as far away as possible from this White House and as far away as possible from anyone that President Trump has appointed."
Unless the administration appoints an independent special prosecutor to probe the Russian meddling, Schumer said, "every American will rightly suspect that the decision to fire director Comey was part of a cover-up."
Ron Wyden, a Democratic Senator from Oregon, was blunt in his criticism.
"Donald Trump's decision to fire him now, in the midst of an investigation into Trump associates and their ties to Russia, is outrageous," he charged.
The stated reason for Comey's dismissal was that he mishandled the probe into Democratic presidential hopeful Hillary Clinton's emails.
But his sacking raised immediate questions about Trump's motives.
Several Republicans approached by AFP about the news, which hit Washington like a thunderclap, declined to criticize the president or Comey directly.
"Given the recent controversies surrounding the director, I believe a fresh start will serve the FBI and the nation well," said Senator Lindsey Graham in a statement.
Democrats did not hold back their fury.
"This is nothing less than Nixonian," charged Senator Patrick Leahy, the longest-serving Democrat in the chamber, drawing a parallel with the decision by a crisis-plagued Richard Nixon to fire his attorney general.
"The President has removed the sitting FBI Director in the midst of one of the most critical national security investigations in the history of our country -- one that implicates senior officials in the Trump campaign and administration."
The House Intelligence Committee's top Democrat, Adam Schiff, echoed those concerns, saying the dismissal "raises profound questions about whether the White House is brazenly interfering in a criminal matter."
"To take this action without addressing the profound conflict of interest of the President and Attorney General harkens back to a similarly tainted decision by President Nixon."
Democrat Mark Warner, vice chairman of the Senate Intelligence Committee, said it was vital to rebuild "trust" in the Justice Department, which oversees the FBI, by appointing an independent special counsel.
That call was echoed by Leahy, among others.
"There simply is no avoiding the compelling fact that this cascading situation demands the prompt appointment of an independent special counsel to pick up the pieces of these investigations."