U.S. Ambassador Samantha Power says the United States is trying to determine whether the commander of the elite Quds Force in Iran's Revolutionary Guard recently visited Russia in violation of a United Nations travel ban.

Power said the travel ban requires all countries to prohibit Maj. Gen. Ghasem Soleimani from traveling to their nation, and the only exception is if the Security Council committee monitoring sanctions against Iran grants an exemption.

"To our knowledge no such exemption was granted, and we would know," Power told reporters Friday. "So these are very concerning reports but we are still, again, tracking down the facts."

A spokesman for Iran's U.N. Mission had no immediate comment and the Russian mission did not immediately return a message seeking comment.