Russian strikes damage a residential building in Kharkiv's Saltivka district in Ukraine. AFP

The situation in the eastern Ukrainian region of Kharkiv is "difficult" but Ukraine's forces are repelling Russian attacks and have re-taken several square kilometres on the eastern front over the past week, a deputy defence minister said on Monday.

The Ukrainian military said last week that Russia was attacking towards Kupiansk, a town in the Kharkiv region.

"The situation in the Kupiansk direction is difficult. The enemy is not leaving plans to move forward, the enemy is pulling up additional forces," Hanna Maliar told the national television broadcaster.

"We are confident in our defenders, but it is very difficult for them there and the enemy is not advancing there," she said.

Maliar said that Ukrainian forces were advancing south of Bakhmut, the city occupied by Russian forces in May after a bloody months-long struggle, and had liberated another three square kilometres over the past week.

Reuters was not able to verify the reports.

This photo shows a destroyed apartment in a heavily damaged residential building following Russian strikes in Kharkiv. AFP

Maliar said there were no significant changes in the situation in the south, where Ukrainian forces are trying to split Russian forces and reach the Sea of Azov.

"We should not underestimate the enemy," Maliar said. "We should all be patient and support our armed forces."

The Ukrainian military said on Thursday it had made gains on the southeastern front, pushing forward from the newly liberated village of Urozhaine.

However, a U.S. official said last week Ukrainian forces did not appear likely to be able to reach and retake the Russian-occupied strategic southeastern city of Melitopol during their counteroffensive.

Reuters