YANKTON, S.D.(WNAX)- There is growing concern that Russian dictator Vladimir Putin could resort to some type of nuclear attack in hopes of reversing his military position in Ukraine.

South Dakota Senator John Thune says they have had briefings about that possibility.

Thune says the Russians are losing ground.

Thune says it’s a national security issue.

Russia unleashed a number of rocket attacks across Ukraine Monday, in response to an explosion on a key bridge this weekend.