KYIV, UKRAINE • Advancing Russian forces came closer to surrounding Ukrainian troops in the east, briefly seizing positions on the last highway out of a crucial pair of Ukrainian-held cities before being beaten back, a Ukrainian official said on Thursday.

Three months into its invasion of Ukraine, Russia has abandoned its assault on the capital Kyiv and is trying to consolidate control of the industrial eastern Donbas region, where it has backed a separatist revolt since 2014.

Thousands of troops are attacking from three sides to try to encircle Ukrainian forces in Sievierodonetsk and Lysychansk. If the two cities straddling the Siverskiy Donets river fall, nearly all of the Donbas province of Luhansk would be under Russian control.

“Russia has the advantage, but we are doing everything we can,” said General Oleksiy Gromov, deputy chief of the main operations department of Ukraine’s general staff.

Luhansk governor Serhiy Gaidai said around 50 Russian soldiers had reached the highway and “managed to gain a foothold”, even setting up a checkpoint.

“The checkpoint was broken, they were thrown back ... the Russian army does not control the route now, but they are shelling it,” he said. It was possible Ukrainian troops would leave “one settlement, maybe two. We need to win the war, not the battle,” he said.

“It is clear that our boys are slowly retreating to more fortified positions - we need to hold back this horde,” Gaidai added.

Western military analysts see the battle for the two cities as a potential turning point in the war, now that Russia has redefined its principal objective as capturing the east.