Russian-backed forces have made tactical advances in the last three days towards the center of Bakhmut, a strategically important town in the eastern Donetsk region, and likely advanced into villages south of the town, Britain said on Friday.
Bakhmut sits on a main road leading to the cities of Sloviansk and Kramatorsk.
Private military company Wagner Group "likely remains" heavily involved in the Bakhmut fighting, Britain's Ministry of Defence said in an intelligence bulletin.
In Ukraine's Donbas region, the ministry said that Russia continued with offensive operations in the central part of the state and was "very slowly" making progress.