The head of the FBI has for the first time publicly confirmed that federal investigators are looking into both Russia’s alleged interference with the 2016 election and also possible links between Moscow and members of Donald Trump’s campaign team.

The US media has for months reported that the bureau was probing possible collusion between Russia and the team of the New York businessman.

But amid a background of leaks, innuendo and allegations of so-called fake news, FBI Director James Comey not only confirmed the existence of such an investigation, but also said it would not be completed for some time.

Mr Comey, who was criticised by many Democrats for his revelation late in the 2016 election campaign that a probe into Hillary Clinton’s use of a private email server had been reopened, told the House Intelligence Committee there was only so much he could say in a public setting.

He said the probe, which he said began in July, included “investigating the nature of any links between individuals associated with the Trump campaign and the Russian government and whether there was any coordination between the campaign and Russia's efforts”.

He added: "Because it is an open, ongoing investigation and is classified, I cannot say more about what we are doing and whose conduct we are examining.”

Earlier, the chairman of the committee, Republican Representative Devin Nunes, told the same hearing that the panel had seen no evidence of collusion between Russia and Mr Trump's 2016 campaign.

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Mr Nunes also repeated his opinion that there was no evidence to support a claim by the billionaire businessman that there had been a wiretap on his Trump Tower in New York but said it was possible other surveillance was used against the Republican.

Other congressional committees also are investigating a possible Russian connection mostly behind closed doors.

The US government alleged last summer that Russian intelligence had tried to interfere with the presidential election, in an apparent attempt to help Mr Trump. This included hacking into the emails of senior members of Hillary Clinton’s team and the Democratic National Committee.

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Mr Trump long rejected the claim that Russia had came to his assistance. Moscow also denied the allegations. In late December, Mr Obama expelled 35 Russian diplomats in punishment for the alleged interference. Vladimir Putin surprised many by deciding not to reciprocate.

Mr Trump has continued to insist there was collusion between his campaign and Russia, and US intelligence has yet to provide any evidence to support such an allegation.

Mr Comey was asked whether he had yet uncovered anything to support such a conclusion. He responded by saying that he would not be able to comment until the probe was concluded - something he said would not happen quickly.

“All I can tell you is that we are investigating whether there was any collusion or coordination between Russia and the Trump campaign,” he said.

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Mr Comey’s revelation will be seized on by supporters of Ms Clinton, furious with the FBI Director’s 11th hour intervention in the 2016 campaign, something the party believes tipped the election in Mr Trump’s favour.

“Some folks made a comparison to past instances where the Justice Department and the FBI has spoken about the details of some investigations,” Mr. Comey said.