Russian forces have temporarily eased their attacks on the besieged eastern Ukrainian city of Bakhmut to regroup and strengthen their capabilities, a senior Kyiv official said on Saturday.

Russia's Wagner private army began handing over its positions to regular Russian troops this week after declaring full control of Bakhmut following the longest and bloodiest battle of the war.

In a statement on Telegram, Deputy Defence Minister Hanna Maliar said Russian forces have continued attacking but that "overall offensive activity has decreased".

"Yesterday and today there have not been any active battles - neither in the city nor on the flanks," she wrote, adding that Moscow's troops were instead shelling the outskirts and approaches to Bakhmut.

"The decrease in the enemy's offensive activity is due to the fact that troops are being replaced and regrouped," Maliar said. "The enemy is trying to strengthen its own capabilities."

She added that Ukrainian troops "firmly hold" the heights overlooking Bakhmut from the north and south, as well as a portion of the outskirts, but have not advanced during the past two days to focus on "other tasks".

The commander of Ukraine's ground forces, Oleksandr Syrskyi, posted a video on Saturday which he said depicted Ukrainian special forces operating inside the ruined city.

Kyiv is expected to soon launch a highly anticipated counteroffensive to retake Russian-occupied territory.

Ukraine's top general posted a sleekly produced video on Saturday showing Ukrainian troops swearing an oath and preparing for battle.

"The time has come to return what is ours," he wrote.