Donald Trump has dismissed claims his campaign team had repeated contact with Russian intelligence officials before the US election as "nonsense".
US intelligence agencies intercepted communications between Trump aides and Moscow around the same time they discovered evidence Russia had hacked into the Democratic National Committee, according to the New York Times.
Citing four US officials, the newspaper said intelligence agencies were investigating "whether the Trump campaign was colluding with the Russians on the hacking or other efforts to influence the election".
The officials - who spoke to the newspaper on condition of anonymity because the continuing investigation is classified - said while they "had seen no evidence of such cooperation", the intercepted communications "alarmed" the US authorities - in part because of Mr Trump’s stated admiration for Russian President Vladimir Putin.
Mr Trump has described the allegations as "nonsense" and claimed they are "merely an attempt to cover-up the many mistakes made in Hillary Clinton's losing campaign".
He also tweeted:
The fake news media is going crazy with their conspiracy theories and blind hatred. @MSNBC & @CNN are unwatchable. @foxandfriends is great!
— Donald J. Trump (@realDonaldTrump) February 15, 2017
Information is being illegally given to the failing @nytimes & @washingtonpost by the intelligence community (NSA and FBI?).Just like Russia
— Donald J. Trump (@realDonaldTrump) February 15, 2017
He added: "The real scandal here is that classified information is illegally given out by 'intelligence' like candy. Very un-American!"
Mr Trump's ex-campaign chief Paul Manafort was named as one of the aides who reportedly had contact with Moscow officials.
Mr Manafort, who is also a former political consultant in Russia and Ukraine, dismissed the claims as "absurd".
"I have never knowingly spoken to Russian intelligence officers, and I have never been involved with anything to do with the Russian government or the Putin administration or any other issues under investigation today," he told the New York Times.
"It's not like these people wear badges that say 'I'm a Russian intelligence officer'."
The Kremlin responded to the allegations by saying they are "not based on any facts".
Michael Flynn resignation
The reports come amid calls for an independent investigation over allegations Mr Trump's national security adviser
Michael Flynn discussed sanctions with Russia's ambassador to the US before he was appointed by the president.
Mr Flynn resigned on Monday, less than a month into the job, as he admitted he gave vice-president Mike Pence "incomplete information" about his phone call with Sergey Kislyak on 29 December.
US Senate Democratic leader Charles Schumer has called for law enforcement officials to question Mr Trump and his staff over "potential criminal action".
He said: "There are potential violations of law here by General Flynn and potentially others.
"Any attempt to lie or mislead must be countered by the full force of the law. (The) resignation raises more questions than it answers. And the American people deserve to know the truth."
On Tuesday, White House spokesman Sean Spicer said the president had been "very concerned" Mr Flynn misled Mr Pence and others.
Mr Spicer said the retired army lieutenant forgot "crucial details" about the call and had also been at fault in a "series of other questionable instances".
The press secretary confirmed the phone call was queried by Justice Department officials on 26th January - the same day General Flynn was reportedly interviewed by the FBI.
