Carter Page is among those targeted according to information gathered by the FBI, CNN reported.
Mr Page, an American oil industry consultant who acted as a foreign policy adviser from the Trump campaign, denied the claim and said he helped US services.
“My assumption throughout the last 26 years I’ve been going there has always been that any Russian person might share information with the Russian government... as I have similarly done with the CIA, the FBI and other government agencies in the past,” he added.
Intelligence officials told CNN Mr Page may have been unaware of the alleged scheme and talked with Russian agents unknowingly.
Court documents said he previously met with a spy called Victor Podobnyy in 2013, who attempted to recruit Mr Page and was later charged as part of ta Russian spy ring.
Documents on the energy industry were handed over but Mr Page said he shared only “basic immaterial information and publicly available research documents”.
He has also visited Russia several times, interacting with officials the FBI believe act on behalf of the Kremlin and delivering a university lecture in 2016 where he accused US of “condescending” and “hostile” policies towards Russia.
On returning to the US, Mr Page was among the Trump campaign advisers meeting with Russian ambassador Sergey Kislyak on the sidelines of the Republican National Convention.
The FBI later got a warrant under the Foreign Intelligence Surveillance Act (Fisa) to monitor Mr Page’s communications.
Officials from Mr Trump’s campaign said there was no indication Mr Page attended national security meetings at Trump Tower and played only a junior role.
CNN’s report claimed Russia attempted to infiltrate Mr Trump’s campaign by using “backdoor channels” to his inner circle, with US and European intelligence finding several advisers had been in contact with known Russian agents.
It came after the Kremlin rejected a Reuters investigation alleging that a think tank controlled by Vladimir Putin drew up a plan to swing the presidential election in Mr Trump’s favour.
The Moscow-based Russian Institute for Strategic Studies (RISS) dismissed claims it was part of a Russian influence campaign as “fantasies”.
Mr Putin’s spokesman, Dmitry Peskov, attacked the use of anonymous sources while dismissing the allegations, originating from current and former American officials citing RISS documents.
Russia has repeatedly denied interfering in the US election, while Mr Trump has also rejected a report by his own intelligence agencies on the campaign.
Barack Obama’s administration concluded that Russia mounted a “fake news” drive and launched cyber attacks against Democratic Party groups and Hillary Clinton’s campaign.
Ongoing congressional and FBI investigations into Russian interference have so far produced no public evidence that Mr Trump’s associates colluded with the Russian effort to change the outcome of the election.