Russian forces have tried to make further advances in the Donetsk region and shelled several towns, including Bakhmut and nearby Soledar and Opytne
The General Staff of the Ukrainian Armed Forces added that Russian forces took up defensive positions and trained tank, mortar and artillery fire on Ukrainian positions and in Kherson city.
“We are analysing the intentions of the occupiers and preparing countermeasures – tougher countermeasures than is now the case,” President Volodymyr Zelenskyy said
The Russian military has said it wants "another way" to access Moldova's breakaway Trans-Dniester region. Meanwhile, the UN chief is set to travel to Moscow next week to meet Vladimir Putin.
Ukraine's army said on Thursday it was worried about the "growing threat" of a new Russian offensive from Belarus.
Moscow and Minsk launched a joint military exercise this week, with thousands of Russian troops gathering in Belarus over the past few days.
Belarus, which is Ukraine's northern neighbour, served as a rear base for Russian forces during the first wave of their invasion in February. A joint training exercise preceded this.