Russian forces claim they are on the verge of capturing the key city of Bakhmut in eastern Ukraine.

Fighters with the Wagner Group private military company have been spearheading the assault.

CNN and Reuters news agency say they were able to confirm a video released by Wagner appears to show its mercenaries just 2 kilometers from the city center.

Ukrainian field hospitals nearby have been inundated with soldiers wounded in the fight to hold Bakhmut.

The US-based Institute for the Study of War says Russian troops appear to be focusing their offensive in one part of the city to force the Ukrainians to retreat.

Earlier this week, a Ukrainian official told CNN a "strategic withdrawal" is on the table.

Many civilians living in the area are fleeing for safety as fighting heats up.

Meanwhile, the US-based Center for Strategic and International Studies has reported a grim milestone.

It estimates between 60-to-70-thousand Russians died or went missing over the last year.

That's more than the combined number of all Russians killed in any conflict since the end of World War Two.

Moscow's official number of combat deaths stands at just under 6-thousand, which it hasn't updated since last September.