The White House shocked Washington by announcing that James Comey “has been terminated and removed from office”.
But Democrats said he was fired because the FBI was investigating alleged links between the Trump campaign and Russia.
The move came as it emerged Mr Comey gave inaccurate information to Congress last week about Mrs Clinton’s emails.
An FBI investigation into her use of a private email server to store sensitive information while secretary of state remains closed. Mr Comey said in July last year it was careless but not criminal.
The White House said the search for a successor for Mr Comey would begin immediately. It is only the second time the head of the FBI has been fired.
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