New York Times :Ukraine’s fragile new government accused Russia of trying to provoke a military conflict on Friday by invading the Crimea region, while in Washington President Barack Obama issued a stern warning to the Kremlin about respecting Ukraine’s sovereignty, apparently in an effort to preclude a full-scale military escalation.US officials did not directly confirm a series of public statements by senior officials in the new Ukrainian government, including its acting president, Oleksandr Turchynov, that Russian troops were being deployed to Crimea, where Russia has a major naval base, in violation of the two countries’ agreements there.Obama, however, cited “reports of military movements taken by the Russian Federation inside of Ukraine,” and he said, “Any violation of Ukrainian sovereignty would be deeply destabilizing.””There will be costs,” Obama said in a hastily arranged statement from the White House.The pointed warning came after a day in which military analysts struggled to understand a series of unusual events in Crimea, including a mobilization of armored personnel carriers with Russian markings on the roads of the region’s capital, Simferopol, and a deployment of well-armed masked gunmen at Crimea’s two main airports.”The Russian Federation began an unvarnished aggression against our country,” Turchynov said in nationally televised remarks Friday evening. “Under the guise of military exercises, they entered troops into the autonomous Republic of Crimea.”He said Russian forces had captured the regional parliament and the headquarters of the regional government, and they had seized other targets, including vital communications hubs, as well as blocked unspecified Ukrainian military assets.US officials said they believed that unusual helicopter movements over Crimea were evidence that a military intervention was underway, but cautioned that they did not know the scale of the operation or the Russians’ motives.