President Barack Obama said Friday that reports that Russia had moved into Ukraine's Crimea region could be "deeply unstabilizing" to Europe and prevents the nation from determining its own fate.
"We are now deeply concerned about military movements taken by the Russian federation in Ukraine," Obama told reporters.
News reports out of Ukraine, indicate pro-Russia gunmen were patrolling streets in the Russian-majority region in armored vehicles, seizing airports. Telecommunications between Crimea and the rest of Ukraine shut down.
Ukraine Interior Minister Arsen Avakov had characterized the presence of the unidentified armed men as an armed invasion.
U.S. officials said Russian assured them that the military activities were routine and not intended to threaten the nation's sovereignty or incite violence.
But Obama said Russia's involvement could be described "profound interference."
"The Ukrainian people deserve the opportunity to determine their own future," Obama said. "Human beings have the universal right to determine their own future."
The remarks came after ousted Ukrainian President Viktor Yanukovych resurfaced in Russia, insisting he remained his country's legitimate elected leader.
Obama spoke from the White House Briefing Room about the growing crisis in Ukraine in a hastily called speech late Friday.
Earlier in the day, White House press secretary Jay Carney called reports that Russia was poised to intervene in Crimea of "deep concern" to the U.S. and said it would be a "grave mistake" for Russia to take that step.
"We strongly support Ukraine's territorial integrity and sovereignty, and we expect other nations to do the same," Carney said.