Ukrainian officials said their forces advanced to the outskirts of Donetsk on Saturday in an attempt to retake the stronghold held for months by pro-Russia rebels. The move comes as Ukrainian forces appear to have gained some momentum in retaking control of territory from the rebels. But Russia also appears to becoming more involved in the fighting, with the U.S. and Ukraine accusing Moscow of moving artillery across the border to the rebels. Donetsk, a city of about 1 million people, is a major center of the separatist uprising that has battled Ukrainian government forces for five months.
