The United States added Igor Sechin, the head of Russia's state-controlled energy major Rosneft, to its Ukraine-related sanctions list on Monday, the U.S. Treasury Department's website said, according to Reuters.

Sechin, a powerful ally of Russian President Vladimir Putin, is the most senior energy executive to be targeted by U.S. sanctions so far.

The sanctions did not name Rosneft itself. Rosneft jumped to the top of the global production league last year with a $55 billion acquisition of rival TNK-BP. BP Plc's share price was down 1.5 percent after the announcement.