Ukraine has stopped production at its coking coal mine in Pokrovsk, which feeds the country's steel industry, because of the proximity of advancing Russian forces, two industry sources told Reuters on Monday.

MOSCOW/KYIV (Reuters) -Russian forces are closing in on the strategically important eastern Ukrainian city of Pokrovsk after capturing a string of villages to its south, and Ukraine has halted production at its only coking coal mine nearby due to the advance.

The Russian army is strengthening its positions in villages around the key eastern Ukrainian town of Pokrovsk in an attempt to encircle it and lay siege to a vital transport hub linking embattled Donbas with the rest of Ukraine.