Ukraine has pulled back troops near several villages in the northeastern Kharkiv region, where Russian forces have been advancing and pounding settlements along the border since last week, Kyiv announced.

Moscow launched a surprise major ground assault on the region last week as it seeks to advance across the battlefield with Kyiv struggling for arms and manpower.

"In some areas, around Lukyantsi and Vovchansk, in response to enemy fire and assaults from ground troops, and to save the lives of our servicemen and avoid losses, our units maneuvered and moved to more advantageous positions," the Ukrainian military announced overnight between Tuesday and Wednesday.

The two villages, around 30 kilometers (18 miles) apart, are close to the border with Russia and have been targeted in the fresh offensive.

Kyiv has rushed reinforcements to the area to prevent Russia from punching through.

Some military analysts say Moscow may be trying to force Ukraine to divert troops from other areas of the front line, such as around the strategic town of Chasiv Yar in the Donetsk region, where Russia has also been advancing.

"Donetsk and Kharkiv regions are where it is most difficult now," Ukrainian President Volodymyr Zelensky said in an address on Tuesday evening.