"The situation on the eastern front has deteriorated significantly in recent days" in the face of a heightened Russian offensive, Ukraine's commander-in-chief Oleksandr Syrsky said Saturday.

Syrsky, who took over as commander-in-chief in February after Ukrainian President Volodymyr Zelensky fired his popular predecessor, Valery Zaluzhny, said Russians also had superior weapons.

He spoke of "a significant intensification of the enemy's offensive after the presidential elections in Russia," in the middle of March and added that decisions were being taken "to strengthen the most problematic defense areas with electronic warfare and air defense".

Ukraine has 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 kilometers (12 miles) west of Bakhmut, which was flattened by months of artillery fire before it was captured by Moscow last May.

Russia has recently secured its first territorial gains since seizing Bakhmut and is now 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 with assault groups supported by armoured vehicles. In the Pokrovsk sector, they are trying to break through our defence using dozens of tanks and armored personnel carriers," Syrsky said.

He said Russia was "stepping up its efforts by deploying new armored units, which periodically achieves tactical success.

"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 and create conditions for seizing the strategic initiative," he said.

"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," he added.