First, FBI director James Comey told the House Intelligence Committee that there was no evidence to back up Trump's Twitter claims that Obama had wiretapped Trump Tower during the 2016 campaign.

In this clip, both Comey and National Security Agency head Michael Rogers tell the committee that they don't have evidence that Russian Federation interfered with the voting process in swing states last fall.

The committee is investigating, among other things, Russian hacking that intelligence officials have said was meant to influence the election.

Like he said publicly last week, Nunes said there was no wiretap at Trump Tower in NY, as the president asserted in a series of tweets earlier in the month.

His tweet came as Federal Bureau of Investigation and National Security Agency chiefs were to speak to Congress on what ties Mr Trump may have with Russian Federation and his as yet unsubstantiated claim that he was wiretapped by his predecessor, Barack Obama.

"Also, is it true that the DNC would not let the Federal Bureau of Investigation in to look?" he said, suggesting without evidence that his Democratic rival Hillary Clinton's campaign may have some connections with Russian Federation.

Though Comey would not discuss specific evidence, he went far beyond his testimony from a hearing in January, when he refused to confirm or deny the existence of any investigation exploring possible connections between Trump associates and Russian Federation, consistent with the FBI's longstanding policy of not publicly discussing its work.

Ever since Trump was inaugurated on January 20, there have been questions and rumors about links between members of Trump's campaign and the Russian government.

But he added, in opening comments to a House Intelligence Committee hearing looking at the matter, that "because it is an open ongoing investigation and is classified, I can not say more".

"We know there was not a physical wiretap of Trump Tower", he said.

"I've got a tweet from the president an hour ago", Himes said, reading the tweet. Trump aide Omarosa Manigault said Monday on Fox News' "Fox & Friends" program. "We have been closely monitoring Russia's aggressions for years", Nunes said.

Nunes said the leaks were "clearly designed" to hurt General Michael Flynn, who briefly served as President Trump's national security adviser.

Later, Comey clarified his Patriots comment, stating New England "represent (s) sustained excellence, and as a Giants fan that drives me insane". "President Trump owes the American people and President Obama more than just an explanation, but an apology".

Mr Trump also suggested, without evidence, that Mrs Clinton's campaign was in contact with Russian Federation and had possibly thwarted a federal investigation.

Trump also said there is no evidence to suggest he worked with Russian Federation.

"Senior Obama intelligence officials have gone on record to confirm there is NO EVIDENCE of Trump-Russia collusion and there is NO EVIDENCE of a Trump-Russia scandal", the official said.

The top Republican and Democrat on the House Intelligence Committee differed in public statements on the evidence of collusion Sunday.