Ukraine's army leader admitted on Sunday that Kyiv's position on the battlefield has worsened after Russian forces captured another village in the east, pressing their advantage in manpower and ammunition.

Russia's troops are advancing in the eastern Donetsk region as Kyiv awaits the arrival of much-needed US weapons that it hopes will stabilise the fragile front lines.

"The situation at the front has worsened," Ukrainian commander-in-chief Oleksandr Syrsky said in a Facebook post on Sunday.

Ukrainian troops had "retreated" westwards to new defensive lines in a section of the front that runs past the city of Donetsk, controlled by pro-Russian forces since 2014.

Russia has "a significant advantage in forces and means" and had been able to notch up advances amid "heavy fighting," Syrsky said.

"In some sectors the enemy had tactical success, and in some areas our troops managed to improve the tactical position," he added.

Russia's defence ministry earlier on Sunday claimed its troops had captured the village of Novobakhmutivka in the Donetsk region – around 10 kilometres north of Avdiivka, which they seized in February.

The stark assessment of the picture facing Ukrainian troops comes at the end of week of ups and downs for Kyiv.

The United States finally approved a US$61 billion package of financial aid after months of political wrangling, unlocking much-needed arms for Ukraine's stretched troops.

But on the battlefield Russia chalked up more successes.

Its troops managed to make rapid advances in a narrow column to the northwest of Avdiivka. (AFP)