Washington: Three key figures, including the founder of a Russian gun rights group, refused to submit to interviews or produce documents requested by Senate Democrats investigating whether the Kremlin used the National Rifle Association to boost Donald Trump's 2016 presidential campaign.

Nonetheless, Democrats on the Senate Judiciary Committee said in a report on Wednesday that their preliminary investigation turned up "a number of documents" suggesting Russia used connections to the NRA "as a means of accessing and assisting Mr Trump and his campaign."

Members of the National Rifle Association (NRA) hold hands during an opening prayer at the NRA annual meeting in Dallas, Texas Credit:Bloomberg

"The Kremlin may also have used the NRA to secretly fund Mr Trump's campaign," the minority report concluded.

While qualified, the findings align with a news report in January that the FBI was investigating whether a top Russian banker funnelled money to the powerful gun lobby group to aid Trump's underdog campaign.