The U.S. military believes a buildup of Russian forces near the border with Ukraine, seen as “concerning” on March 30, is likely a training exercise. But the gathering of troops comes amid heightened tension in the region, and Ukraine’s Commander-In-Chief Ruslan Khomchack told his country’s parliament this week that Russian forces from different regions had been assembling near the border.
Russia's War Against Ukraine
CBS News: US watching ‘escalation of armed confrontation’ near Ukraine’s border with Russia

(FILES) A convoy of Russian-backed forces' 2S1 Gvozdika (122-mm self-propelled howitzers) drives from the frontline near the eastern Ukrainian city of Starobeshevo in Donetsk region, on Feb. 25, 2015.