Russia's defence ministry says its forces thwarted a major Ukrainian offensive in the Donetsk region but a mercenary leader said Russian troops had lost ground around Bakhmut further north.
Asked whether the attacks represented the start of Ukraine's long-heralded counter-offensive against Russia's invasion, Oleksiy Danilov, Secretary of Ukraine's Security and Defence Council, told Reuters: "The war continues. Until complete victory."
Russia's defence ministry said Ukraine had attacked on Sunday morning with six mechanised and two tank battalions in southern Donetsk, where Moscow has long suspected Ukraine would seek to drive a wedge through Russian-controlled territory.
"On the morning of June 4, the enemy launched a large-scale offensive in five sectors of the front in the South Donetsk direction," the defence ministry said in a statement posted on Telegram at 1.30am Moscow time on Monday.
"The enemy's goal was to break through our defences in the most vulnerable, in its opinion, sector of the front," it said. "The enemy did not achieve its tasks, it had no success."
Asked to comment, a Ukrainian military spokesperson said: "We do not have such information and we do not comment on any kind of fake."
Further north, near the long-contested city of Bakhmut, Ukrainian forces were reported to have been "moving forward" by the commander of Ukraine's ground forces, Oleksandr Syrskyi.
An armed forces video showed Russian positions under fire and Russian mercenary leader Yevgeny Prigozhin said Ukrainian forces had retaken part of the settlement of Berkhivka, north of Bakhmut in eastern Ukraine, calling it a "disgrace".
Prigozhin's private Wagner army captured Bakhmut last month after the longest battle of the war and handed its positions there to regular Russian troops.
The daily report from Ukraine's General Staff said only there were 29 combat clashes in the Donetsk and Luhansk regions of eastern Ukraine, while Ukraine's Centre for Strategic Communications said Russia would seek to spread lies.
"To demoralise Ukrainians and mislead the community (including their own population), Russian propagandists will spread false information about the counter-offensive, its directions, and the losses of the Ukrainian army," it said.
Russia's defence ministry released video of what it said showed several Ukrainian armoured vehicles in a field blowing up after being hit. Reuters geo-located it to near Velyka Novosilka, a village west of Vuhledar in southern Donetsk region, but could not verify the date.
"There is a tough fight going on," wrote prominent Russian military blogger Semyon Pegov, who blogs under the name War Gonzo, saying Ukrainian forces were attacking in the area.
The ministry said Russian forces killed 250 Ukrainian troops as well as destroying 16 tanks, three infantry fighting vehicles and 21 armoured combat vehicles. Reuters was not able to verify the figures. Both sides have exaggerated casualties suffered by the other.
Ukrainian President Volodymyr Zelenskiy told the Wall Street Journal in an interview published on Saturday that he was ready to launch a counter-offensive but tempered a forecast of success with a warning that it could take some time and come at a heavy cost.
