Trump fires FBI director James Comey, setting off US political storm

US President Donald Trump ignited a political firestorm on Tuesday by firing FBI Director James Comey, who had been leading an investigation into the Trump 2016 presidential campaign's possible collusion with Russia to influence the election outcome.

In a shock move that drew comparisons to the Watergate scandal that brought down Richard Nixon, Trump told Comey the FBI needed new leadership and he was being "terminated" with immediate effect.

He said the move was over his handling of an election-year email scandal involving then-Democratic presidential nominee Hillary Clinton.

Under Comey's leadership, the FBI also concluded that President Vladimir Putin approved a wide-ranging campaign to tilt the vote in Trump's favour.

In a letter circulated by the White House, Trump told Comey: "You are hereby terminated and removed from office, effective immediately."

"It is essential that we find new leadership for the FBI that restores public trust and confidence in its vital law enforcement mission."

Trump's decision to fire the FBI director is virtually unprecedented, only one director has previously been fired in the bureau's century-long history.

His snap dismissal, sparked rare criticism from Republicans and allegations of a cover-up from Democrats who argued the White House was trying to blunt the FBI probe involving Russia. They demanded an independent inquiry.

Some Democrats compared Trump's move to the "Saturday Night Massacre" of 1973, in which President Richard Nixon fired an independent special prosecutor investigating the Watergate scandal.

Senate Democratic leader Chuck Schumer said he spoke to Trump and told him he was "making a very big mistake" in firing Comey, adding the president did not "really answer" in response.

An independent investigation into Moscow's role in the election "is now the only way to go to restore the American people’s faith," Schumer said.

Though many Democrats have criticised Comey's handling of the Clinton email probe, they said they were troubled by the timing of Trump's firing of him.

Senator Richard Burr, the Republican chairman of the Senate Intelligence Committee, which is overseeing its own investigation into Russian interference during the election, said in a statement he was also troubled by the timing of Comey's termination.

"His dismissal, I believe, is a loss for the Bureau and the nation," Burr said.

White House officials denied allegations that there was any political motive in the move by Trump, who took office on 20 January.