U.S. Sen. James Lankford said he has no doubt Russia stepped up its efforts last year in an attempt to sway and discredit the presidential election. But the Republican member of the Senate Intelligence Committee said he has yet to see any evidence of cooperation between President Donald Trump's 2016 campaign and the Russian government.

"At this point, the accusations are troubling," Lankford, R-Oklahoma City, told The Oklahoman in a telephone interview this week. "We are looking for any evidence behind it. We are trying to figure out what are the facts behind it."

The Intelligence Committee has begun an investigation into allegations that Trump campaign officials were in contact with Russian officials during last year's presidential campaign.

The New York Times first reported U.S. intelligence officials had discovered last year that Trump adviser Michael Flynn and campaign chairman Paul Manafort were in contact with Russian officials.