Russian military analysts list Sloviansk, Kramatorsk, Druzhkivka and Kostiantynivka as the "fortress cities" in Ukraine's east accessible from Chasiv Yar if Moscow's forces can get there, something Kyiv is determined to stop.

Russia said on Thursday it had captured the town of Chasiv Yar in eastern Ukraine after nearly 16 months of fighting, opening the way for potential further advances. Russia's Defence Ministry said in a brief statement its forces had "liberated" the town.

Russian forces cannot capture Chasiv Yar in the Donetsk region on the move. Ukrainian troops maintain fire control over all approaches where Russians attempt assaults, said Ukrainian 11th Army Corps Spokesperson Lieutenant Colonel Dmytro Zaporozhets.