By Jonathan Landay DERGACHI, Ukraine (Reuters) – Ukrainian forces destroyed parts of a Russian armoured column as it tried to cross a river in the Donbas region, video from Ukraine’s military showed on Friday, as Moscow appeared to be refocusing its assault in the east after a new pushback by Kyiv. Ukraine has driven Russian troops away from the second-largest city of Kharkiv in the fastest advance since Kremlin forces pulled away from Kyiv and the northeast over a month ago, although Moscow is still bombarding villages north of Kharkiv. The city, which had been under fierce bombardment, has b…