The statement by Colonel General Oleksandr Syrskyi on Sunday reflected Ukraine's deteriorating position in the east that Kyiv hopes it can stabilise once it takes delivery of US weapons under a $US61 billion ($A93 billion) aid package approved this week.
"The situation at the front has worsened," he wrote on the Telegram app, describing the "most difficult" areas as west of occupied Maryinka and northwest of Avdiivka, the town captured by Russian forces in February.
Ukraine's top commander Oleksandr Syrskyi says his troops' position in the east is deteriorating. (EPA PHOTO)
Kyiv's troops, he said, had taken up new positions west of the villages of Berdychi and Semenivka, both north of Avdiivka, and Novomykhailivka, further south near the town of Maryinka.
"In general, the enemy achieved certain tactical successes in these areas, but could not gain operational advantages," Syrskyi said, adding that Russia had committed four brigades to the assault.
Freshly rested Ukrainian brigades were being rotated in those areas to replace units that had suffered losses, he said.
His statement did not mention the status of Novobakhmutivka, another village near Berdychi, that Russia's defence ministry said on Sunday its forces had captured.
Moscow's troops have been slowly advancing since capturing the bastion town of Avdiivka, taking advantage of Ukrainian shortages of artillery shells and manpower.
Online battlefield maps produced by open-source intelligence analysts suggest they have advanced more than 15 km in the direction of the village of Ocheretyne since capturing Avdiivka.
Further up the front, the Kyiv-held town of Chasiv Yar is a key emerging battleground because of its position on elevated ground that could serve as a gateway to the cities of Kostiantynivka, Sloviansk and Kramatorsk.
Syrskiy described Chasiv Yar and the village of Ivanivske to its northeast as the "hottest spots" on that part of the front. Russia's defence ministry said it had repelled Ukrainian counter-attacks near Chasiv Yar.
In what could prove a worrying development for Ukraine, Syrskiy said his forces were closely monitoring an increase in the number of Russian troops in the area of Kharkiv, Ukraine's second largest city.
Russian rockets targeted a regional psychiatric hospital in Kharkiv. (EPA PHOTO)
The northeastern city of 1.3 million just 30 km from the Russian border has been hammered by air strikes in recent months in what Kyiv has said is a deliberate effort by Moscow to make Kharkiv uninhabitable.
Syrskiy said there were so signs that Russia was directly preparing for an offensive in the north of the country.
"In the most threatening directions, our troops have been reinforced by artillery and tank units," he said.
Ukraine is currently expecting a long-awaited a shipment of US military aid which officials say is critical to holding off Russia's two-year-old invasion.
A Ukrainian intelligence source told Reuters this week that Russia was conducting air strikes on Ukrainian rail lines to disrupt the delivery of US weapons to the front and to complicate military logistics.
