The affected senior officials included the deputy head of the State Duma, or parliament, the minister of the Crimea, a commander of the Russian intelligence agency FSB, and a Ukrainian separatist leader.

"We have emphasized our preference to resolve this issue diplomatically," Obama said. "We have to see concrete actions, not just words, that Russia in fact is committed to trying to end this conflict."

He said Russia had continued to support separatists in east Ukraine, sending fighters and weapons across the border.

Obama in recent weeks has repeatedly threatened new sanctions, and appears to have run out of patience as fighting continued to rage in eastern Ukraine.

The new sanctions were unlikely to please Republican lawmakers, many of whom have been calling for the imposition of sanctions on entire Russian industries, rather than specific companies, as the best way to control Russian President Vladimir Putin.

Washington said on Wednesday that up to 12,000 Russian forces were back on the border with Ukraine and that weaponry was crossing over to pro-Russian separatists.

"These are combat forces," Pentagon spokesman Colonel Steve Warren told reporters. The increase in the Russian presence occurred several weeks after Moscow had drawn down its forces in the area to about 1,000 troops.

Rosneft, Russia's largest oil company, had no immediate comment. Morgan Stanley, which is selling the majority of its global physical oil trading operations to Rosneft, declined to comment. (rt/ez)