Ukraine's commander-in-chief Oleksandr Syrsky said Saturday the situation on the eastern front had worsened significantly and Russia claimed the capture of a village near the occupied industrial town of Avdiivka.
"The situation on the eastern front has deteriorated significantly in recent days," said Syrsky, who took over as commander-in-chief in February after Ukrainian President Volodymyr Zelensky fired his popular predecessor, Valery Zaluzhny.
Russia's defence ministry announced its troops had "liberated" the village of Pervomaiske in the Donetsk region, about 11 km (7 miles) west of the largely destroyed town of Avdiivka, captured by Russia in the middle of February.
Ukraine has not confirmed this. Its army said Friday that it had repelled attacks on the village.
Syrsky spoke of "a significant intensification of the enemy's offensive after the presidential elections in Russia" last month.
The commander-in-chief added decisions were being taken "to strengthen the most problematic defence areas with electronic warfare and air defence".
In the southern Zaporizhzhia region, Russia accused Ukraine on Saturday of killing 10 by shelling the occupied town of Tokmak.
The town fell to Russia at the start of the invasion.
Ukrainian authorities in Zaporizhzhia said Russia had struck the region more than 400 times over the last day, including from planes.
Ukraine has also said the situation around the eastern frontline city of Chasiv Yar is "difficult and tense" with the area under "constant fire".
Chasiv Yar lies 20 kilometres west of the town of Bakhmut, which was flattened by months of artillery fire before it was captured by Moscow last May.
Russia is now securing fresh territorial gains and trying to press onwards against Ukrainian units hobbled by delays in the supply of vital Western military aid.
"The enemy is actively attacking our positions in the Lyman and Bakhmut sectors ... In the Pokrovsk sector, they are trying to break through our defence using dozens of tanks and armoured personnel carriers," Syrsky said.
"The issue of achieving technical superiority over the enemy in high-tech weapons has again arisen. Only this will enable us to defeat a larger enemy," Syrsky said.
- Training push -
"The second serious problem is to improve the quality of training of military personnel, especially infantry units, so that they can make the most of all the capabilities of military equipment and Western weapons," Syrsky added.
European allies of Ukraine are engaged in a training push for its forces.
France's defence minister Sebastien Lecornu on Friday said future Ukrainian fighter pilots likely to fly American F-16 aircraft were receiving their initial training in the south of France.
Other countries including the Netherlands, Denmark and Romania are seeking to help Ukraine train pilots.
Some Ukrainians, after receiving initial training in Britain, are now undergoing "advanced training" in an undisclosed location to learn how to fly fighter jets, according to a military source.