Ukraine braces for heavy battles as Putin says Russia carving out 'buffer zone'

Ukraine's top commander warns of intense fighting in the Kharkiv region, where Russian forces are advancing to create a buffer zone. President Putin denies plans to capture Kharkiv but justifies the incursion due to alleged Ukrainian shelling of Russian border areas. Ukrainian forces brace for potential assaults in Sumy. Both sides engage in airstrikes and drone attacks.