Subsequent satellite images from Planet Labs showed a plume of smoke covering nearby Proletarsk’s far western edge, almost six miles away.

Late on Sunday, Vasily Golubev, the governor of Rostov, wrote in a post on the Telegram messaging app that emergency workers were still trying to extinguish the fire. He said three firefighting trains had been brought in to take the blaze.

Unverified footage circulated on social media on Monday showed the night skies around an industrial site illuminated by bright orange flames.

It was shared by the News161ru account on Telegram, and was purported to have been sent to the outlet by readers. Witnesses said the flames were visible more than 55 miles away, the social media account added.

The Telegraph could not confirm whether the video was shot from Proletarsk and when it was taken.