A US senator on Wednesday said Russian internet trolls were stoking the NFL debate to try and stir up divisiveness in America.

Hundreds of sports stars have taken the knee in protest since President Trump declared on Friday that NFL players who refused to stand during the national anthem were 'sons of b***hes' and should be fired.

Since then, the hashtags #TakeAKnee and #BoycottNFL have been trending and the movement has been picked up by celebrities, scientists and doctors who have shared pictures of them kneeling in solidarity on social media.

On Wednesday, Sen. James Lankford, of Oklahoma, claimed that Russia had paid social media trolls to stoke the debate in an attempt to polarize America. He said they have been sharing the hashtags 'take a knee' and 'boycott NFL' to amplify the issue and spread discord.

'We watched, even this weekend, the Russians and their troll farms, their internet folks, start hashtagging out #TakeAKnee and also hashtagging out #BoycottNFL,' Lankford, who sits on the Senate Intelligence Committee, said during a hearing on threats faced by the United States.

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Sen. James Lankford (pictured) said Russian internet trolls were stoking the NFL debate to try and stir up divisiveness in America

Terrance Smith #48, Eric Fisher #72, Demetrius Harris #84, and Cameron Erving #75 of the Kansas City Chiefs are seen taking a knee before the game against the Los Angeles Chargers Sunday afternoon, in protest over Trump's comments

Hundreds of sports stars have taken the knee in protest since President Trump declared on Friday that NFL players who refused to stand during the national anthem should be fired (Members of the Detroit Lions take a knee on September 24, in Detroit)

'We watched, even this weekend, the Russians and their troll farms, their internet folks, start hashtagging out #TakeAKnee and also hashtagging out #BoycottNFL,' Lankford, who sits on the Senate Intelligence Committee, said during a hearing on threats faced by the United States.

'They were taking both sides of the argument this weekend ... to try to raise the noise level of America and make a big issue seem like an even bigger issue as they are trying to push divisiveness in this country,' Lankford said.

Lankford did not provide evidence to corroborate his statement.

The claim comes as congressional investigators who are probing Moscow's alleged meddling in the 2016 presidential election, focusing on how Russian agents used social media to spread divisive political content.

President Donald Trump last week referred to NFL players who kneel during the anthem as 'sons of b******'

A Lankford aide said U.S. intelligence shared with senators showed that Russian troll operations relied on social media to meddle in U.S. issues going back to last year's presidential election in an effort to divide Americans.

Such activity has also been occurring in Europe for years, the aide said.

A website built by researchers working with the Alliance for Securing Democracy, a bipartisan, transatlantic project to counter Russian disinformation, showed tweets promoting both sides of the football debate from 600 accounts that analysts identified as users who spread Russian propaganda on Twitter.

A Senate aide said the website was viewed as credible among congressional investigators.

Earlier this month, Facebook acknowledged hundreds of fake accounts, probably run from Russia, spent about $100,000 on ads aimed at stoking divisive issues such as gun control and race relations during the election.

Executives from Facebook , Alphabet Inc's Google and Twitter will appear in the US Congress in the coming weeks as lawmakers probe Russia's alleged interference in the 2016 US election, committee sources said on Wednesday.

Lawmakers are increasingly alarmed about evidence that hackers used the internet to spread fake news and otherwise influence the 2016 election, have been pushing for more information about the influence of social networks in particular.

As a member of the Senate intelligence committee, Lankford is privy to intelligence that Russian troll farms have used social media to create doubt and chaos in U.S. institutions and government, according to a congressional aide. The aide, who was not authorized to speak publicly, spoke only on condition of anonymity.

Earlier this month, Facebook acknowledged hundreds of fake accounts, probably run from Russia, spent about $100,000 on ads aimed at stoking divisive issues such as gun control and race relations during the election

Facebook revealed recently that it sold $100,000 worth advertisements to possible Russia-linked buyers (Pictured: Russian President Vladimir Putin Sept. 27, 2017)

The NFL controversy has been a hot topic in the news recently.

President Donald Trump has spent days lashing out at players who kneel during the national anthem, a practice that started with a handful of players to protest racial issues, including police brutality.

Clint Watts, who helped create a website that tracks Russian propaganda on social media, said he can't yet say with certainty that Russian trolls were a major force in the NFL protest debate — after all, plenty of Americans also weighed in. But he suspects Lankford is right.

Watts, a senior fellow at the Foreign Policy Research Institute, said it would be consistent with other documented propaganda campaigns that originated in Russia, such as the use of Facebook to push messages for and against the Black Lives Matter movement.

'The goal is heightened tensions,' Watts said. 'They'll use organic American content to amplify to American audiences. They would much rather use organic American content. It hits the audience better and it's cheaper and more effective.'

Trump, who triggered the debate on Friday, is the perfect vehicle for 'active measures' campaigns, a Soviet term for information warfare designed to destabilize democracies from the inside, Watts said.

'The Russians can just sit back and say: 'Amplify on both sides. Make people angry.' And it works, man, God, it works,' Watts said.

He also said: 'The goal is to sow division in America.'

Russia denies seeking to influence the U.S. election, and Trump has dismissed claims of collusion as fake news.