FBI director James Comey has confirmed an investigation into Russian hacking is also exploring whether there was coordination between Donald Trump’s campaign and the Kremlin.
The bombshell was an unusual move given the FBI does not usually comment on ongoing investigations.
“But in unusual circumstances, where it is in the public interest,” Mr Comey said, “it may be appropriate to do so.”
Mr Comey also dismissed the president’s claims that Barack Obama ordered the wiretapping of Trump Tower.
Both he and NSA director Admiral Mike Rogers emphatically rejected claims GCHQ had carried out the surveillance on behalf of the Obama administration.
They said that would be a violation of US law and that the accusation “frustrates the relationship with a key ally”.
Both men were speaking at the first Congressional intelligence committee public hearing on alleged Russian interference in the 2016 election.
For months it has been the consensus of the US intelligence community that Russian used a portfolio of propaganda including hacking and ‘fake news’ to hurt Hillary Clinton’s campaign and help Mr Trump.