“Fierce fighting continues along the front lines. Our defenders are firmly holding their positions and inflicting losses to the enemy,” said Oleh Synehubov, governor of the northeastern region of Kharkiv.
Reuters could not verify battlefield reports.
Oleskandr Musiyenko, head of the Military and Strategic Research Centre of Ukraine, said Russia was sending in more reinforcements to block Ukrainian advances.
“They are mostly sending infantry and artillery forces into battle, made up mainly of conscripts. But they do not have the level of artillery and tank support they had on Feb 24,” Musiyenko told Ukrainian television.
“They have fewer resources. They are relying on the numerical superiority of their troops.”
Russia’s invasion has killed thousands of civilians, uprooted millions and reduced cities to rubble.
Front lines have remained largely frozen over the past two months, with Russia trying to gain more ground in the east after occupying much of what is known as the Donbas region and protect a corridor of land it has occupied in southern Ukraine.
Britain said in a regular intelligence update on Friday that Russian forces had probably conducted probing attacks near Orikhiv in the southeast and in Vuhledar in the east, but were unlikely to have achieved “substantive advances.”
Both sides are widely expected to launch a spring offensive.
“Where will the main (Russian) strike occur? For now, we have no idea. Diversionary strikes are possible in all sectors and, in one or two, mass strikes aimed at punching a corridor through Ukraine,” Mykola Sunhurovskiy, director of military programmes at Ukraine’s Razumkov Centre think tank, told the nv.ua website.
Russia has in the past reacted to Ukrainian successes with heavy air strikes that left millions without light, heat or water.
On Thursday, it appeared to follow that pattern. Prime Minister Denys Shmyhal said Russia’s attacks targeted energy plants.