The Ukrainian government has urged people in Russian-occupied southern areas of the country to evacuate “by all possible means” in advance of a Ukrainian military offensive as Moscow’s forces were described as creating a “true hell” in Ukraine’s eastern industrial heartland, officials said.

The governor of Luhansk, Serhiy Haidai, said on Saturday that Russian forces had mounted 20 artillery, mortar and rocket attacks in the province overnight and Russians were pressing towards the border with neighbouring Donetsk.

“We are trying to contain the Russians’ armed formations along the entire front line,” Haidai wrote on Telegram, describing the attacks in terms of a “true hell”.

Last week, Russia captured the last major stronghold of Ukrainian resistance in Luhansk, the city of Lysychansk, and analysts had predicted that Moscow’s troops likely would take an “operational pause” to rearm and regroup its forces.