Ukrainian forces have stopped Russian troops advancing in the northeastern Sumy region and are now battling along the border to regain control, President Volodymyr Zelenskyy said.
In remarks released for publication by his office on Saturday, Zelenskyy said that Moscow has amassed about 53,000 troops in the direction of Sumy.
"We are leveling the position. The fighting there is along the border. You should understand that the enemy has been stopped there. And the maximum depth at which the fighting takes place is 7 km from the border," Zelenskyy said.
Reuters could not verify battlefield reports.
Russia's troops have been focusing their assaults in the eastern Donetsk region, but since the start of the month, they have intensified their attacks in the north-east, announcing plans to create a so-called 'buffer zone' in the Sumy and Kharkiv regions.
The Russian war in Ukraine is in its fourth year but it has intensified in recent weeks.
Ukraine conducted an audacious drone attack that took out multiple aircraft inside Russia and also hit the bridge connecting Russia to the annexed Crimean peninsula using underwater explosives.
Zelenskyy said that the Ukrainian troops had maintained their defensive lines along more than 1,000 kilometers of the frontline. He also dismissed Moscow's claims that Russian troops had crossed the administrative border of the Ukrainian central region of Dnipropetrovsk.
Zelenskyy said that Russia was sending small assault groups "to get one foot on the administrative border" and make a picture or a video but these attacks were repelled.
Dnipropetrovsk region borders three regions that are partially occupied by Russia – Donetsk, Kherson and Zaporizhzhia. Russia now controls about one-fifth of Ukrainian territory.
Zelenskyy acknowledged that Ukraine was unable to regain all of its territory by military force and reiterated his pleas for stronger sanctions on Russia to force Moscow into negotiations to end the war.
Two rounds of peace talks between Kyiv and Moscow in Istanbul produced few results that could lead to a ceasefire and a broader peace deal. The two sides agreed only to exchange prisoners of war.
Several swaps have already been conducted this month, and Zelenskiy expected POW swaps to continue until June 20 or 21.
Ukrainian officials responsible for exchanging prisoners of war said on Saturday that Kyiv had received the bodies of 1,200 of its soldiers killed in the war with Russia. The bodies were handed over to Ukraine on Friday.
"The agreement is that the exchanges will be completed, and the sides will discuss the next step," Zelenskyy said.