Responding to strong advances by the Ukrainian military against separatist insurgents in the week since the downing of a passenger jet, Russia has stepped up its direct involvement in the hostilities in eastern Ukraine, Ukrainian and American officials say, unleashing artillery attacks on Ukrainian positions from Russian territory and amassing heavy weapons along the border that Kiev and its allies fear could be pushed across to reinforce the rebels and prolong the fighting.
Russia's War Against Ukraine
New York Times: Russia said to shell Ukraine and mass arms along border
Russian border guard soldiers man a foxhole near a checkpoint on Ukrainian border in the southern Russian Rostov region on June 21, 2014.
