Earlier, Serhiy Haidai, the governor of the Donetsk region, said Russian forces had taken control of the villages of Kremenaya and Lugashchnine, both north-west of the town of Severodonetsk.

“Evacuation from there is already impossible,” he wrote on Telegram early on Monday morning. Residents of Luhansk were warned that this was their last chance to evacuate.

Ukraine on Sunday launched a counter-offensive designed to cut supply lines to Izyum, where Russia appears to be massing troops for the northern trust of an encirclement of Donbas, the mainly Russian-speaking and heavily industrialised region where war broke out in 2014.

The Russian military said on Monday its missiles had struck more than 20 military targets in eastern and central Ukraine over the past day as it stepped up a campaign to hit weapons factories, railways and other infrastructure targets before the offensive.

Residents of Vasylkiv, a town south of Kyiv that is home to a military airbase, reported a large explosion on Monday morning.

Russian missiles also hit Lviv, killing at least seven people, according to Maksym Kozytsky, its regional governor.

“At the moment, we are able to confirm that seven people have died. We also know that 11 people are injured. A child is among them,” he said. “Three victims are in critical condition.” He confirmed there were four missile strikes with three hitting military infrastructure and one a tyre shop.