Colonel Oleksandr Motuzyanyk, the Defense Ministry spokesperson, said Russia was carrying out "intense fire and assault operations along the entire line of combat confrontation in Donetsk and Luhansk regions."

Read here Severodonetsk: the fiercest battles continue

Seven aircraft had launched guided missiles from above the Black Sea and Caspian Sea, while coastal missile systems in Crimea were also active.

On the ground, Motuzyanyk said the Russians had made some advances, including north of Sloviansk, where they were advancing in the Sviatohirsk area toward the Siverskiy Donets River. He said the Russians were carrying out "engineering reconnaissance of the area, preparing for the possible forcing of a water barrier." But in other districts on this front they had been repulsed, he said.

Sloviansk and Severodonetsk

Sloviansk is a key target of the Russian operation, and Russian forces have been edging closer to the city in recent weeks.

Further east in Severodonetsk, Motuzyanyk said Ukrainian units were holding back "the offensive of the Russian aggressor, who seeks to surround our troops in the area of Severodonetsk and Lysychansk, as well as to block the main logistics routes.....Units of the Armed Forces of Ukraine are fighting hard against the occupiers in the eastern and central parts of the city. The enemy spares neither people nor equipment. With the support of artillery, the enemy conducts assault operations to achieve its goal of taking control of the city," he said.