Spanish police have turned over to the FBI wiretaps of conversations involving Alexander Torshin, a prominent Russian banker suspected of money laundering who met with President Donald Trump's eldest son, Donald Trump Jr., during the 2016 US presidential election.

Torshin is closely associated with the National Rifle Association, and he and his longtime assistant attempted to use the organization's annual convention in 2016 to set up a backdoor meeting between Trump and Russian President Vladimir Putin.

Neither Trump nor his campaign associates attended the convention, but Torshin and Trump Jr. did attend a separate NRA dinner that same night.

When José Grinda, a Spanish prosecutor who spearheads investigations into organized crime, was asked if he was concerned about Torshin's interactions with Trump Jr. or other American political figures, Grinda replied: "Mr. Trump's son should be concerned."

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The FBI has obtained wiretaps from Spanish authorities of conversations involving an ally of Russian President Vladimir Putin who met with President Donald Trump's eldest son, Donald Trump Jr., during the 2016 US presidential election, Yahoo News reported.

Alexander Torshin is a prominent Russian banker, politician, and gun-rights activist who is closely tied to the National Rifle Association. He has long been on the Spanish government's radar for his suspected involvement in money laundering and organized crime, and media reports earlier this year indicated that the FBI was investigating whether Torshin used the NRA as a vehicle to funnel Russian money into the election to boost Trump.

José Grinda, who has led investigations by the Spanish government into organized crime in the country, said this week that the FBI had in recent months requested and received transcripts of wiretapped conversations between Torshin and Alexander Romanov, a former Russian banker with connections to the mob who has been convicted of money laundering.

Grinda said Spanish authorities had turned over the transcripts featuring Torshin to the FBI "a few months ago," and that Romanov referred to Torshin on the tapes as "El Padrino," or the godfather.

Torshin and his longtime assistant, fellow Russian gun-rights activist Maria Butina, have attracted scrutiny over their attempts to set up backdoor meetings with senior members of the Trump campaign during the election.

In particular, Butina has cultivated her own ties with the American gun-rights activist and Republican strategist Paul Erickson, whom she has been acquainted with since at least 2013.

Erickson came under scrutiny last year, when The New York Times reported that he emailed Trump campaign aide Rick Dearborn in May 2016, with the subject line "Kremlin Connection," telling him that he could arrange a backdoor meeting between Trump and Putin.

Erickson added that Russia would try to make contact with the Trump campaign at the NRA's annual convention in Louisville, Kentucky, that month.

Torshin was designated to make "first contact" with Trump from Russia's side. Erickson described him in his email as "President Putin's emissary on this front."

Erickson wrote that Torshin would make contact with the campaign at a dinner honoring wounded veterans that was organized by the conservative Christian advocate Rick Clay. Neither Trump nor his campaign advisers attended the reception. However, Torshin and Trump Jr. attended a separate NRA dinner the same night.

When Grinda was asked whether he was concerned about Torshin's interactions with Trump Jr. and other American political figures, Grinda replied, "Mr. Trump's son should be concerned."

Trump has said neither he nor his campaign colluded with Moscow. The Trump administration also denied in 2017 that Trump had met Torshin.

But a number of tweets sent from Torshin's Twitter account, which NPR reviewed in depth in February, appeared to indicate otherwise.

Torshin tweeted in November 2015 that he knew "D. Trump (through NRA). A decent person." He later added that he saw Trump in Nashville, Tennessee in April 2015. The NRA held its annual convention in Nashville that year, during which Trump gave a speech teasing his impending presidential bid.

"If I run, and people are going to be very surprised, and if I win, America will be great again," Trump told the approving crowd, which included Torshin and Butina, who spearheads a Russian gun-rights group, The Right to Bear Arms.

Torshin attended the NRA's convention every year between 2012 and 2016, occasionally with Butina at his side, and has met every NRA president since 2012. Through his connections to the group, Torshin was selected to be an election monitor during the 2012 US presidential election. And when the NRA sent a delegation to Moscow in the winter of 2015, it was Torshin who received them on behalf of The Right to Bear Arms.

In February 2017, Torshin was also invited, through his NRA ties, to a national prayer breakfast with the newly-inaugurated President Trump. According to Yahoo News, Torshin was scheduled to meet Trump before the event, but his invitation was rescinded after a White House aide spotted his name on the guest list and alerted others to Torshin's murky financial background.