At the moment, they need physical and psychological help," Striuk added.

Avalanche of missile strikes

Ukraine has been hit by an avalanche of missile strikes, with official accounts there estimating that Russia fired more than 40 missiles at targets in Ukraine in the past 24 hours.

The General Staff of the Ukrainian military said there was more shelling around Kharkiv, and the Russians had tried to launch an assault near the settlement of Uda, north of Kharkiv, but "were decisively suppressed by our soldiers." 

North of Sloviansk, the Ukrainian military reported continuing battles in areas that have been on the front lines for months.

Regional authorities in Lviv in western Ukraine also reported missile strikes against military facilities.

Offensive continues in eastern Ukraine

Two US officials with direct knowledge of US intelligence assessments told CNN Russian forces were gaining an advantage in eastern Ukraine as they learned from mistakes made during the earlier stages of their invasion of the country, including better coordination of air and ground attacks as well as improvements to logistics and supply lines.

Meanwhile, Ukrainian troops in the eastern city of Lysychansk are under growing pressure from Russian forces that have taken territory to the south of the city.

If they capture Bakhmut they would be able to prevent most resupply efforts to Ukrainian defenders in Lysychansk and surrounding districts. 

Ukraine claims attacks launched from Belarus airspace

As Ukrainian authorities assessed the damage from dozens of missile strikes overnight, the Defense Ministry's Main Intelligence Directorate said that many of the missiles were fired from Belarusian airspace.

The Directorate said that "missile strikes from the territory of Belarus are a large-scale provocation of the Russian Federation in order to further involve Belarus in the war against Ukraine."

It said '"Russian bombers hit directly from the territory of Belarus.

CNN cannot confirm that allegation.

Ukraine's air force command has echoed the Defense Ministry's comments, saying on its Facebook page that "more than fifty missiles of various types were fired: air, sea and ground-based."

There has been no word from the Belarus government on the alleged use of its airspace for the latest strikes against Ukraine.

Ukraine denies Russian claim of attack on Polish 'mercenaries'

A Russian missile hit the town of Kostiantynivka in Donetsk Saturday, according to both local authorities and the Russian Ministry of Defense.

But the two sides' versions of what was targeted differ. Oleksii Roslov, head of Kostiantynivka civil military administration, said an "object of critical infrastructure was hit," affecting gas supply and killing one person.

The Russian Ministry of Defense published a short video of the missile attack, saying it targeted Polish mercenaries based at the Megatex plant in Kostiantynivka and had killed up to 80 of them, as well as rocket launchers. 

Russian Defense Ministry spokesman, Lieutenant General Igor Konashenkov, said: "The enemy continues to suffer significant losses.