The people who described the alleged proposal said they didn't attend the December meeting and didn't have direct knowledge from Mr. Flynn or his associates about its purported details.
Flynn is a central figure in Mueller's investigation because of conversations he had with then-Russian Ambassador Sergei Kislyak previous year and because he waited until March to retroactively register with the Justice Department as a foreign agent for the work he did for a Turkish businessman.
Special Counsel Mueller is reportedly looking into an alleged plot involving former National Security Adviser Michael Flynn and a plan to forcibly remove a Muslim cleric from the United States and send him to Turkey. These include Flynn's partners, Bijan Kian and Brian McCauley, and Flynn's son, Michael G. Flynn.
Mueller, who is leading the investigation into Russia's interference in the 2016 USA election and whether President Donald Trump's campaign colluded with Moscow to tilt the race in his favor, has compiled enough evidence to bring charges against Flynn and his son, NBC News reported on Sunday.
If Mueller and his team suspect Flynn tried to take official actions to benefit a foreign government, then anyone who tried to impede the investigation into Flynn's alleged misconduct might also face accusations of wrongdoing. "We should not provide him safe haven".
He is now the center of criminal, military and congressional investigations that seek to unearth a possible connection between that and his decisions while he was the president's adviser.More news: Mitt Romney blasts Roy Moore as 'unfit for office'
Special counsel Robert Mueller is leading an investigation looking into the Trump campaign's supposed ties to Russian Federation during the 2016 election.
The Journal reported that Federal Bureau of Investigation agents asked at least four people about a December meeting in NY where Flynn and Turkish government representatives discussed removing Gulen, according to people with knowledge of the FBI's inquiries.
Multiple sources have told NBC News that Mueller has gathered enough evidence to lead to an indictment in the investigation into Flynn and his son.
"Out of respect for the process of the various investigations regarding the 2016 campaign, we have intentionally avoided responding to every rumour or allegation raised in the media", Flynn's lawyer Robert Kelner told the press.
This meeting was held in December - after the USA presidential election and during Donald Trump's transition period - as Flynn was preparing to oversee national-security policy at the White House.
Flynn, a retired lieutenant general who was previously head of the Defense Intelligence Agency, became the White House national security advisor after Trump took office on January 20, 2017.