The Ukrainian military has acknowledged Russian advances in some areas in the east of the country — though it says the extent of the progress is difficult to measure.
In its daily operational update, the General Staff said Russian forces had crossed the Siverskiy Donets river in the direction of Lyman, which is in the Donetsk region.
Lyman is a town to the northeast of Sloviansk, one of the Russians' strategic objectives. Several bridges across the river had been brought down during earlier fighting. CNN is unable to quantify the scale of the Russian advance.
"In the Sloviansk direction, the occupiers are regrouping troops to resume the offensive on Barvinkove and Sloviansk. The enemy moved the battalion tactical group in order to strengthen the advanced units," the update said.
CNN has previously reported that Russia has added further battalion tactical groups to its offensive in this area.
The General Staff also said that further east "the enemy is advancing in the direction of Kudriashivka bear Severodonetsk; with partial success ... Their main task is to establish full control over Rubizhne, to capture Lyman and Severodonetsk."
Kudriashivka is a small settlement close to Severodonetsk and Rubizhne, where Ukrainian forces have been holding off a Russian advance for weeks. The humanitarian situation in Severodonetsk, where some 15,000 people still live, is said to be dire.
River crossing attempts in Luhansk: The regional military administration in Luhansk said that "in total, towns and villages of Luhansk region were fired at 26 times during May 11. The largest number was in Severodonetsk."
The Russians have repeatedly tried to cross the Siverskiy Donets in this area, but Ukrainian forces have quickly destroyed several pontoon bridges in recent days, according to a CNN analysis of satellite imagery. The General Staff said Thursday that another attempt to cross the river was being made near Kreminna.
If the Russians were able to sustain a river crossing, Ukrainian troops in the Severodonetsk area would be vulnerable to being cut off.
Northeastern battles: In the Kharkiv region, a Ukrainian counterattack continues, and the General Staff says the Russians are reinforcing units in the border area.
"The enemy is regrouping troops in order to prevent a further advance of our troops in the direction of the state border. ... In the areas north of Kharkiv city, the enemy fires artillery at units of our troops."
Line holds to the south: In the south of Ukraine, the Ukrainian military reports further shelling by Russian forces but no changes in frontline positions. The authorities in Dnipro said there had been shelling throughout the night and one civilian had been killed.
UK weighs in: The UK Defense Ministry commented Thursday that "Russia’s prioritisation of operations in the Donbas has left elements deployed in the Kharkiv Oblast vulnerable to the mobile, and highly motivated, Ukrainian counter-attacking force. Despite Russia’s success in encircling Kharkiv in the initial stages of the conflict, it has reportedly withdrawn units from the region to reorganise and replenish its forces following heavy losses."
