Acting Department of Homeland Security Secretary Elaine Duke, FBI Director Christopher Wray and National Counterterrorism Center Director Nicholas Rasmussen appear before a Senate committee Wednesday. (Melina Mara/The Washington Post)

Russian Internet trolls are trying to gin up even more controversy over NFL players taking a knee during the national anthem, a senator said Wednesday — warning that the United States should expect such divisive efforts to escalate in the next election.

Sen. James Lankford (R-Okla.) made the assertion in a hearing with the heads of the FBI, Department of Homeland Security and the National Counterterrorism Center.

Russian trolls, he said, were cynically pushing both sides of the argument over whether players should take a knee at the playing of the national anthem before NFL games. Players have been doing so as a silent protest against police treatment of minorities, though critics — including President Trump — argue that doing so disrespects the American flag and members of the U.S. military.

“We watched even this weekend, the Russians and their troll farms, and their Internet folks, start hash-tagging out ‘take a knee’ and also hash-tagging out ‘Boycott NFL,’ ’’ Lankford said.

The Russians’ goal, the lawmaker said, was “to try to raise the noise level in America to try to make a big issue, an even bigger issue as they’re trying to just push divisiveness in the country. We’ve continued to be able to see that. We will see that again in our election time.’’

The witnesses at the hearing, including the new head of the FBI, Christopher A. Wray, did not speak directly to Lankford’s assertion.

Wray did say that the FBI is expanding its efforts to track Russian attempts to influence U.S. elections.

“We are surging more resources, specifically focused on the upcoming elections,’’ he said. “We are collecting more intelligence. One of the things we know is that the Russians and Russian state actors are trying to influence other elections in other countries.’’

U.S. intelligence agencies have said Russia sought to influence the outcome of the 2016 election, and they expect those efforts to be repeated in future elections.

Lankford’s spokesman said the senator, as a member of the Intelligence Committee, has been receiving information on Russian troll farms and bots for more than a year, and such actors routinely seize on divisive topics in U.S. politics.

“Senator Lankford made an individual decision to start talking about this publicly, because he believes the American people should know,’’ said the spokesman, who also offered an example of what he said was a Russian Twitter account calling itself Boston Antifa that gives its geolocation as Vladivostok, Russia.

“More gender inclusivity with NFL fans and gluten free options at stadiums,” the tweet read. “We’re liking the new NFL #NewNFL #TakeAKnee #TakeTheKnee.”

The Washington Post reported earlier this week that Russian-bought Facebook ads during last year’s election season sought to exploit social, racial and religious divisions in the United States.

Some of the ads promoted African American rights groups, including Black Lives Matter, while others suggested those same groups posed a growing political threat, according to people familiar with the material.

The campaign season ads also sought to send contrary messages to different user groups based on their political and demographic characteristics, and to sow discord among religious groups. Officials said the ads show how sophisticated the efforts were to mimic and sway U.S. political discourse while exacerbating preexisting tensions among different groups of Americans.

U.S. officials have warned that Russia is applying a propaganda tactic that dates back to the Cold War — trying to exploit divisions within the United States by amplifying arguments that already exist. Experts have warned that social media platforms give Russia a greater ability to do so.