The White House slapped down calls for a special prosecutor to investigate allegations that Donald Trump's campaign colluded with Russia, after the US president abruptly fired his FBI director.
Trump's shock dismissal of James Comey -- the man overseeing federal investigations into suspected Kremlin interference in the 2016 vote -- has sparked a political firestorm in Washington and plunged his young presidency in turmoil.
Furious Democrats suggested the FBI's work will now be hopelessly tainted and demanded a special prosecutor akin to those appointed during Richard Nixon's Watergate scandal or the run-up to Bill Clinton's impeachment.
"We don't think it's necessary," said White House spokeswoman Sarah Huckabee Sanders, batting back that demand.
Sanders said the White House wanted the FBI probe -- and parallel congressional investigations -- to continue and to wrap up their work. "No one wants this to be finished and completed more than us."
The White House says Comey's firing was motivated solely by concerns over his handling of the high-stakes probe into Hillary Clinton's emails.
A US official said the president had been "losing confidence" in his FBI chief for several months, and that after watching Comey testify before Congress as part of the Russia probe last week Trump was "strongly inclined to remove him."
Read more: Trump dismisses FBI Director James Comey
The president personally defended his summary dismissal of Comey and rejected suggestions it was linked to the Russia investigation.
"He wasn't doing a good job, it's very simple, he was not doing a good job," Trump told reporters as hundreds of demonstrators gathered outside the White House chanting "shame on you!"
His comments came shortly after Trump hosted Russia's top diplomat at the White House, in his highest-level Kremlin encounter since taking office.
Trump described an Oval Office meeting with Sergei Lavrov, the highest-profile Kremlin official to visit the White House in years, as "very, very good."
Under Comey, the FBI concluded that Russia tried to sway the election in Trump's favor through an influence and cyber-hacking campaign.
The bureau has been probing whether Trump's campaign colluded with such an effort -- something the president rejects as "fake news."
Lavrov, who last set foot in Washington in August 2013, dismissed all claims of election meddling as "fabrications."
In a sharp new development, the Senate Intelligence Committee announced Wednesday it issued a subpoena to Trump's former national security adviser Michael Flynn for Russia-related documents, which he had previously declined to provide.
Flynn was sacked for lying to Vice President Mike Pence about his discussions with the Russian ambassador to Washington.
Justice Department spokeswoman Sarah Isgur Flores denied reports that Comey had asked for more resources to intensify the probe shortly before being fired.
"(I) don't know how else I can spell this out. The story is just wrong," she told AFP.
Trump's decision to terminate Comey's tenure, effective immediately, stunned Washington and drew comparisons to the Watergate scandal that brought down Nixon.
The Senate's top Republican, Mitch McConnell, on Wednesday dismissed calls for a special prosecutor. He said such an individual would only "serve to impede the current work being done."
But Democratic Senator Richard Blumenthal said even among Republicans there was a "growing feeling of disquiet and doubt about the direction that the president is taking."
He raised the prospect that White House stonewalling on a special prosecutor could trigger a drastic congressional response.
"I would oppose confirmation of a new FBI director until there is support for a special prosecutor," he told reporters.
A defiant Trump took to Twitter to defend his decision, vowing: "James Comey will be replaced by someone who will do a far better job, bringing back the spirit and prestige of the FBI."
"Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike. When things calm down, they will be thanking me!"
But White House officials privately expressed surprise at the level of backlash, particularly from leading Republicans.
Several members of the president's own party, including Richard Burr -- head of the Senate Intelligence committee -- sought to distance themselves from the White House.