By Tom Balmforth and Max Hunder KYIV (Reuters) -Russian forces kept up their bombardment of cities across Ukraine, with intense shelling of Sumy in the north, cluster bombs targeting Mykolaiv and a missile strike in Odesa in the south, authorities said on Tuesday. After failing to capture the capital Kyiv at the outset of the invasion on Feb 24, Russia has shifted to a campaign of devastating bombardments to cement and extend its control of Ukraine’s south and east. Ukraine says Russian forces have intensified long-distance strikes on targets far from the front, killing large numbers of civili…