U.S. Official Says 1,000 Russian Troops Have Entered Ukraine By Victoria Butenko, Laura Smith-Spark and Diana Magnay, CNN August 28, 2014 Kiev, Ukraine (CNN) -- A top Ukrainian army officer said a "full-scale invasion" of his country was under way Thursday, as a U.S. official said up to 1,000 Russian troops had crossed Ukraine's southern border to fight alongside pro-Russian rebels.